ALFALFA IMPROVEMENT

H. M. TYSDAL, Associate Agronomist,
H. L. WESTOVER, Senior Agronomist,
Division of Forage Crops and Diseases, Bureau of Plant Industry¹

[ABSTRACT.]  THE most serious threat to alfalfa growing in the United States is the insidious disease, bacterial wilt, which kills stands of susceptible alfalfa in 2 to 4 years. In the large area where this disease is present—and it is spreading to other areas—it annually destroys hundreds of thousands of acres of alfalfa, with aggregate losses equivalent to those that would be experienced by farmers as a result of flood, drought, or any other major disaster. If varieties or strains could be developed that were sufficiently resistant to maintain stands even 2 years longer, these farmers would be saved many millions of dollars. This is one of the problems on which alfalfa breeders are now working, and promising progress has been made.

ALFALFA means "best fodder" in Arabic, the language from which the crop received its name. Botanically it is known as Medicago sativa L. In England and most other European countries it is called lucerne, perhaps after Lake Lucerne and Lucerne Canton, in Switzerland, where alfalfa was grown at an early date, though some believe the name was derived from the Spanish or the French.

Alfalfa is a member of that large and important group of plants called the legume or pea family, characterized by ability to provide a home for useful bacteria that take nitrogen from the air and store it in a form available to plants, thereby enriching the soil. The home for nitrifying bacteria is on the roots in what are known as nodules, which look like small detachable lumps or knots. The soil-improving value of legumes, combined with their forage values, makes them one of the great economic plant families.

In 1929 alfalfa hay was produced on approximately 35 million acres throughout the world, according to Klinkowski (19). In addition, a proportionately large acreage was devoted to alfalfa-seed production in those regions where climatic and soil conditions are conducive to seed setting and maturity. Argentina reported 14 million acres of alfalfa hay in 1929, the United States nearly 12 million acres (fig. 1), and France 3 million acres. Other countries reported smaller acreages, but the crop was widely distributed. Since 1929 the aggregate acreage of alfalfa is believed to have extended, but there are no available figures to support this belief.

Figure 1.—Distribution of alfalfa production in the United States in 1929. Approximately 11,500,000 acres were cut for hay in that year.

There are many types of alfalfa, and they display wide differences in their adaptation to environmental changes from the Mexican to the Canadian borders and from the arid West to the humid East. They differ not only with respect to soil and climate, but also with respect to their resistance to disease and insect injury.

These differences, long recognized by alfalfa growers and research workers, are now being utilized by plant breeders as the basis of improvement of the crop, and the results of breeding work to date indicate that superior strains can be developed that will make possible an even greater use of alfalfa on the farms of America.

THE best authorities agree that the original home of alfalfa was in southwestern Asia, from Mesopotamia northward across Persia and Turkistan to Siberia. De Candolle (4) states that it has been found wild, with every appearance of being an indigenous plant, in several provinces of Anatolia, to the south of the Caucasus, in several parts of Persia, in Afghanistan, in Baluchistan, and in Kashmir. More recently, Department of Agriculture explorers have found many so-called “wild alfalfas’ in the region of Turkistan, so there can be no doubt that alfalfa got its start in this general region.

Alfalfa was probably planted in this region by half-civilized man ages before any history was written. The earliest records indicate that by that time man had discovered the superior feeding value and soil-building properties of alfalfa. One of the earliest Roman agricultural writers, Columella, stated in De Re Rustica, written about 56 A. D., that all emaciated cattle whatsoever grow fat on it and that it fertilizes the land.

Alfalfa was thus developed in dry regions and was usually found in river valleys with soils rich in lime and of alkaline reaction. Wing (32) has suggested that the grass eaten by Nebuchadnezzar when he was driven into the fields was none other than alfalfa growing in the fertile valley of the Euphrates River near Babylon. The earliest records alluding to alfalfa were discovered in Babylonian text written in 700 B. C. In this reference alfalfa is listed under its Persian name, aspasti, by the gardener of the Babylonian King, Mardukbalidin, which shows that alfalfa was known in the palace grounds of that day.

From this point on the story of alfalfa becomes history. Pliny and Strabo, both early Roman writers, record that when the Medes and Persians invaded Greece in 490 B. C., they introduced alfalfa into that country for the sustenance of their chariot horses, camels, and domestic animals. The plant was named medic, to denote its Median origin, and it has retained this root in the present botanical name, Medicago. This is believed to be the first introduction of alfalfa into Europe. From there it spread to Italy and during the next centuries to other European countries, including Spain. Thus the queen of forage plants, as it has been called, followed the path of historic civilizations and conquering armies from East to West.

The first introduction of alfalfa into the Americas was through the Spanish explorers. When Cortez and Pizarro had completed their conquest, the natives had alfalfa in lieu of their gold. This was at the beginning of the sixteenth century, and alfalfa soon became distributed over Peru and Chile. It is probable, though not certain, that some of the Catholic missionaries brought alfalfa from Mexico into southern California, New Mexico, and Arizona. Be that as it may, there was no decided spread of alfalfa growing in North America at this time.

The English, French, and Germans introduced alfalfa into the colonies of the Atlantic seaboard under the name of lucerne. There was some success in growing it in Virginia, North Carolina, Pennsylvania, and New York, but there were also some disappointments, due, no doubt, to a general lack of well-drained limestone soils and also to lack of knowledge of the necessity of inoculating for nitrogen-gathering bacteria, which, when present, grow on the roots of legumes.  General Washington tried alfalfa at Mount Vernon with enough success to warrant planting a field of it in 1794. Thomas Jefferson, according to Spurrier, took considerable pride in his lucerne field, which was in production prior to 1793.

To trace the further introduction of alfalfa into the United States, it is necessary to return to the west coast, where in the gold rush days of the 1850’s many prospectors came via the all-water route around the Horn to California. Some of them stopped at Chilean ports en route, and, curious as to how this new plant would grow in the new country, took some seed with them. One of the first growers of alfalfa in California, according to the account related by E. J. Wickson to Wing, was W. A. Cameron, of Marysville, in the Sacramento Valley. He produced alfalfa in 1851, and his seed came from Chile.

From the beginning alfalfa produced remarkably good crops in the fertile irrigated valleys of California, and it is not strange that its gradual spread was across the country from the West rather than from the East, because, although it had been grown continuously in New York for over a century, it received its main impetus from the success it had attained in the West. From California it was soon taken to Utah, where the Mormons found it extremely satisfactory. It was then introduced into Colorado, Kansas, and Nebraska. According to the 1916 report of the Kansas State Board of Agriculture (8, p. 11), one of the first successful growers of alfalfa in Kansas was Charles J. Grosse, of Marion, who received his seed in 1868 from the Trumble Seed House on Sansom Street, San Francisco, Calif. In the 1890’s alfalfa had become an important crop in Kansas and spread into Nebraska, where it was also successful. By 1900 it had crossed the Missouri River and become important on the well-drained and alluvial soils of Iowa and Missouri. Then it spread across the Mississippi into Illinois. Wing had previously carried the crop from a ranch in eastern Utah to Champaign County, Ohio, where he established one of the first really successful alfalfa projects in the State.

Considering the historical backgrou=d of alfalfa production in this country, it is probably safe to assume that the so-called Common alfalfa now being extensively grown originated from the early introductions of Chilean alfalfa. It is also evident that through the years the crop has been remarkably changed by natural regional selection.  As indicated by Westover (30), strains developed that have the ability to become relatively dormant in the fall and resist cold, as is the case with Northern Common. Other strains, such as the Common alfalfa found in the South, grow rapidly late in the fall; in other words, they do not respond so greatly to the shortening day length.  Hybridization no doubt has also been a factor in this adaptation, but segregation by survival has been predominant.

At about the time alfalfa was being introduced into California, another circumstance was paving the way for the growing of alfalfa in northern climates. In 1857 Wendelin Grimm brought his family from the Grand Duchy of Baden, Germany, to Carver County, Minn. (figs. 2 and 3). In the spring of 1858 he sowed 15 or 20 pounds of alfalfa seed brought from his native land. This proved to be the origin of what was later called Grimm alfalfa—the first alfalfa grown in this country that had sufficient hardiness to withstand the cold winters of the North. Many attempts had been made to grow the nonhardy alfalfas in Northern States, but this invariably resulted in winter-killing. The advent of Grimm alfalfa greatly increased the acreage importance of the crop.

Figure 2—Mr. and Mrs. Wendelin Grimm, of Chaska, Carver County, Minn. In 1858 Mr. Grimm planted 15 or 20 pounds of alfalfa seed he brought with him from Germany the previous year.  This was the beginning of the present widely grown and popular Grimm alfalfa variety.  (Courtesy of A. C. Arny, Minnesota Agricultural Experiment Station.)



Figure 3—Monument erected in honor of Wendelin Grimm, who greatly benefited northern agriculture by originating the hardy variety that bears his name.  (Courtesy of A. C. Arny, Minnesota Agricultural Experiment Station.)

There can be no doubt that the wide distribution of Grimm today is due to the comparative testing of experiment stations, where its superiority was proved and given publicity. This alfalfa was grown in practical obscurity for almost 50 years before it came to the attention of experiment station officials, after which it was soon widely known. It would be hard to find a better example of the leadership afforded by experiment stations in agricultural work.

The discovery—and it can well be called a discovery, because very little was known regarding the adaptation of alfalfa in this early period—that certain strains were not adapted to certain regions while others thrived there, was an important one. No longer could a prospective grower just ask for alfalfa seed—he had to be sure of the kind of alfalfa seed he was getting. Some confusion thus arose because it was impossible to tell one variety from another by the seed, but fortunately this difficulty has been overcome by certification and verification services made available by State and Federal institutions.

Without doubt, natural selection in alfalfa, helped here and there by the willing hand of man, has taken place for many generations.  This is evident from a comparison of our vigorous-growing, sturdy cultivated alfalfas with the prostrate, slow-growing wild species picked up by plant explorers.  But it must also be admitted that no plant of such value and antiquity shows so little evidence of deliberate breeding.

Only two examples, both cited by Brand (2), 1907, are needed to show what apparently had been accomplished by natural selection, helped along by man. Peruvian alfalfa, which is now grown to a considerable extent in the Southern States, has a very low zero point, that is, ability to grow at a low temperature, but is not at all winter-hardy in northern latitudes. This, Brand suggested, has been due to many centuries of growing in warm climates. On the other hand, it is rather surprising that the original home of Grimm alfalfa in Germany has minimum temperatures less severe than those observed at Albuquerque, N. Mex. From all available records it is clear that the bulk of the original Grimm seed was not sufficiently winter-hardy for Minnesota conditions. Yet by saving seed from the plants that survived each successive winter, generation after generation, the persistent German immigrant, Wendelin Grimm, showed what could be accomplished in the way of acclimatization or adaptation of alfalfa in Minnesota.

In a report of the committee for breeding forage crops, made by Piper (24) in 1909, a very good picture is given of the alfalfa-breeding program in the entire United States at that time.  “It must be borne in mind", the report states, "that alfalfa breeding is a very recent development of plant improvement, apparently no work having been conducted along this line previous to 1903.” At the time of the report 11 workers were directly interested in alfalfa improvement: J. M. Westgate, C. J. Brand, G.W. Oliver, and A.C. Dillman, all of the United States Department of Agriculture; G.F. Freeman, of Kansas; W.H. Olin and P. K. Blinn, of Colorado; F. A. Spragg, of Michigan; E. G. Montgomery, of Nebraska; W. A. Wheeler, of New York: and L. R. Waldron, of North Dakota.

Practically all these workers had a well-developed program, chiefly involving mass selection. Only Oliver, Westgate, and Brand report hybridization of varieties or species, but without definite results.  Two rather distinct methods of selection were followed. Spragg, Dillman, and others selected mother plants without control of the male parent except cutting back adjacent undesirable material at the time of blooming. Olin, Oliver, Brand, and others self-fertilized the selected plants, using wire cages or bagging. This group thoroughly understood the possibility of contamination by cross-fertilization, but apparently they did not fully realize that an individual selected plant might not necessarily—probably would not—pass on all its good characteristics to the next generation. Thus too much effort was often spent in picking out the best plant in the entire nursery, only to find when seed was obtained that the daughter plants were not at all like the mother plant. It must be added, however, that even at this early date many breeders knew the value of the progeny test and used it to determine which was the best parental material.

The workers of this period had a considerable number of strains to use for foundation stock. The State experiment stations had access to the collection of the Department of Agriculture, which included introductions from all important alfalfa-growing regions as well as material from more out-of-the-way parts of the world. The major varieties used were Grimm, Common, and Turkistan. There were also introductions of other species, chiefly Medicago falcata L., and a few species crosses were made, but apparently nothing came of them.

1. Difficulty of keeping strains pure, both during breeding and for increase.
2. Maintaining a large nursery several seasons to await winter-killing or drought to eliminate undesirable individuals.
3. Securing seed.
4. Length of time required to determine the value of any given plant, some suggesting 3 years as the minimum.

The early work can be said to have begun about 1903 and ended about 1915. During this period there was considerable interest in the improvement of alfalfa, one outstanding character sought being winter-hardiness (fig. 4). A group of superior varieties and strains, together with the date they originated, is listed in the appendix, and it may be noted that several of these came into prominence during this early period, notably Grimm, Baltic, Cossack, Ontario Variegated, and Ladak. Figure 5 shows the origin of Ladak and the nursery from which it was selected at the United States Department of Agriculture Experiment Station, Redfield, S. Dak. All of these varieties have superior characteristics, such as cold resistance and adaptation for special conditions. They are all still considered standard varieties.  Introduction and selection played a part in their development.

Figure 4.—A demonstration of the difference in cold resistance of different alfalfas.  Nebraska-grown Common alfalfa at left and Peruvian alfalfa at right, seeded May 16, 1922. Both varieties seemed equally good during 1923 and 1924, but the Peruvian winter-killed almost completely in the winter of 1924-25, while the Nebraska Common was uninjured. Photographed May 25, 1925. (Courtesy of T. A. Kiesselbach, Nebraska Agricultural Experiment Station.)



Figure 5.—The original alfalfa nursery at Redfield, S. Dak., from which Ladak was selected. The seed was sent to the United States Department of Agriculture from the Province of Ladakh, in northern India, in 1910 and was planted in 1914. Photographed July 20, 1915. The entire acreage of the Ladak variety now being grown in the United States came originally from the two rows marked by the arrow. The light color of the rows is caused by the profuse bloom, the preponderance of which was yellow in color. (Courtesy of S. Garver.)

It must be added, however, that many an alfalfa selection was "born to blush unseen” during this period. Some very promising selections made in various nurseries never got any further.  Wheeler’s Grimm No. 19A was increased to the extent of 100 acres, then turned over to farmers and its identity lost. No doubt the worth-while characteristics in this strain have through the years gradually made themselves felt in other strains with which it crossed. Thus the work put into such selections has not been entirely lost.

Nevertheless, the early work did not reach full fruition, for several reasons, among them the World War, which focused attention on the food crops to the detriment of the feed crops, and the widespread introduction of Grimm alfalfa, which largely solved the winter-hardiness problem, wiping out the advantage gained by selection for hardiness in Common alfalfa, and also depriving breeders of a definite goal for selection. In other words, for the moment no great catastrophe threatened alfalfa, and most people, including the breeders, were content to let well enough alone.

But events were already developing that brought a great revival of interest in the improvement of alfalfa and other forage crops.

Crowding into compact communities leads to peculiar problems with plants as with human beings. Growers will tell you they can remember when they could plant alfalfa and leave it down almost any number of years without any trouble. This cannot be done any longer. The problem of winter hardiness was largely overcome by the general use of Grimm and other cold-resistant varieties, but another major problem appeared and became increasingly insistent It manifested itself in the killing out of stands after 2, 3, or 4 years of production. No one knew what was causing the trouble. Finally it became so serious that Department of Agriculture workers undertook to determine the underlying cause.

Finally Jones and McCulloch (15) found the disease was produced by a hitherto unknown organism, a bacterium to which was given the name Aplanobacter insidiosum McCulloch, the insidious Aplanobacter, more recently changed to Phytomonas insidiosa (McCulloch) Bergey et al. The disease it caused was called bacterial wilt. Since its discovery in 1925, apparently increasing inroads have been made by the disease until at the present time it is known to occur from the Atlantic to the Pacific and from the Northern States to the southwestern border. It was apparently most severe in the river valleys of Nebraska and Kansas at first, but it is now found in considerable abundance eastward through Iowa, Illinois, Indiana, Michigan, Ohio, Wisconsin, and other States.

Of the approximately 11½ million acres of alfalfa harvested for hay in the United States in 1934, the 1934 census shows that over 7½ million acres were grown in the 14 North Central States bounded on the east by Ohio and on the west by Colorado. At the present time bacterial wilt is prevalent throughout this region, although it is more serious in some localities than in others. In this region, too, alfalfa is usually allowed to remain as long as there is is a good stand. When it kills out it must be plowed and another field planted to maintain a hay balance. The available domestic alfalfas such as Grimm, Hardigan, and Common are very susceptible to the bacterial wilt disease and kill out, where the disease is severe, in from 2 to 4 years. Figure 6 shows the ravages of bacterial wilt in the domestic varieties in field plots at the Kansas Agricultural Experiment Station.

Figure 6.—Experimental plots at the Kansas Agricultural Experiment Station, Manhattan, Kans., demonstrating resistance or lack of resistance of different varieties to bacterial wilt, the plots with a poor stand being covered with weeds. a, Kansas Common (poor stand); b, Turkistan F. C. 19303 (good stand); ¢, Turkistan F. C. 19304 good stand); d, Grimm (poor stand); e, Ukranian F. C. 19315 (poor stand); f, Turkistan F. C. 19316 (good stand); g, Kansas 308—a resistant selection from Kansas Common. (good stand); h, Dakota Common F. C. 16081 (poor stand); i, Argentine F. C. 15996 (poor stand); j, Cossack F. C. 18836 (fair stand). These plots were slanted in the fall of 1930; photographed September 1936. The greatest decrease in stand took place during the third and fourth years. (Courtesy of C. O. Grandfield, Kansas Agricultural Experiment Station.)

Bacterial wilt annually destroys hundreds of thousands of acres of alfalfa, with aggregate losses equivalent to those that would be experienced by farmers as a result of flood, drought, or any other major disaster. These losses include not only the crop destroyed by the disease but also the cost of seeding and the loss of production from the land until a new crop is established. If, through the use of resistant strains, growers could maintain stands of alfalfa for even 2 years longer, they would be able to save millions of dollars.

Considerable preliminary work indicated that cultural practices in general would not control the disease. The only avenue of approach that offered possibilities was a breeding program. For a number of years Westover and his coworkers, plant explorers of the Department of Agriculture, have been gathering alfalfas from remote parts of the globe. This collection has progressed until at the present time approximately 1,000 different strains of alfalfa are growing in various nurseries in the United States. Some of these were gathered in areas where the natives had never seen or heard of an automobile. Of the alfalfa strains tested from every continent, and almost every country, practically the only strains having decided resistance to bacterial wilt have been found in the region around Russian Turkistan, northern India, western China, and northeastern Persia. Even some alfalfas of the wild type and the Medicago falcata strains found in this region have shown resistance to bacterial wilt. The objective of the breeding program, then, is to combine the good qualities of commercial alfalfas such as Grimm and Common with the bacterial wilt resistance found in the Turkistan alfalfa.

AS ALREADY INDICATED, both new problems and new advances in plant breeding have greatly stimulated alfalfa improvement. At the present time a relatively large number of breeding projects are being started or have recently been started, and there is a great deal of interest on the part of almost all experiment stations, whether or not they are themselves actively engaged in alfalfa-improvement work. In order to make the present status of alfalfa improvement clear, the work that has already been done both in the United States and abroad will be briefly summarized.

   When selection is desired for a certain character, it is often desirable to determine, if possible, what other characters of the plant are associated with it. Sometimes certain characters are inherited together.  By selecting for one, it may then be possible to secure the other also.  This association of characters frequently presents difficulties. In alfalfa, for example, selection for increased forage production usually gives at the same time a more coarse, sparsely leaved plant of poorer quality. In 1914 Freeman (11) published a paper of interest from the standpoint of selection of material. He studied correlations between various characters in alfalfa and, among others, found positive correlations indicating that nitrogen content is associated with the percentage of leaves, and green weight with both the average number of stems and the average height. He found negative correlations indicating that greater forage yield is associated with smaller percentage of leaves; smaller percentage of leaves with greater height; smaller number of stems with greater average height. There was no significant correlation between thickness of stand and percentage of leaves.³  Freeman concludes (11, p. 367):

   In economic plant breeding one frequently encounters physiologically negative correlations such as those, in alfalfa, between height and stooling capacity, height and percentage of leaves, and between yield and quality. In seeking improvement, therefore, the breeder must recognize and malke use of these facts in the interpretation of results obtained, and also search for races which violate such naturally antagonistic correlations to the greatest possible extent.

1. A definite (closed) blooming period
2. Large flower clusters
3. Great individual ability to set seed. (He believes the female parent has a greater bearing on seed productivity than the male.)
4. Many coils per pod with high seed number per pod
5. Least possible shattering of seed

   Other workers, including Kiesselbach and Anderson in Nebraska and Willard in Ohio, have also found a very high correlation between nitrogen content and percentage of leaves. Thus it seems evident that for a higher quality crop it is necessary to have a high percentage of leaves and also that the plant retain those leaves until harvest. Thus disease resistance as well as inherent leafiness is involved, because most of the leaf-spot diseases, for example, tend to defoliate the plant.

   The question of how much crossing naturally occurs in alfalfa brings such different answers that there is obviously no exact information on the point. Waldron found 42.7 percent crossing between purple and yellow, the yellow being the female parent, while he found 7.5 percent crossing in the reciprocal, the purple being the female parent. As high as 80 percent crossing has been observed in Nebraska between closely associated plants of the purple-flowered (Medicago sativa) and yellow-flowered (M. falcata) alfalfa, the female again being yellow. It is more difficult to determine the crossing between purple-flowered strains of similar origin because of the difficulty of determining when a cross is obtained. This difficulty is now being overcome in the production of “testers" by at least three experiment stations. These include a strain produced by the South Dakota station with pure white flowers, the character acting as a simple recessive. Another strain produced at the Wisconsin station has red roots, also simply inherited; and the Nebraska station has a strain producing four or five leaflets instead of the usual three. These strains all have the M. sativa type of flower, and by their use reliable information should be obtained on the amount of natural crossing, the distance necessary for isolation, and possibly on the activities of various insects.

A considerable body of facts bearing on the question of the influence of self-fertilization on an alfalfa population is gradually being established. The work of Kirk (17), Williams (31), Torssell (26), Dann (7), and others suggests, on the whole, decrease in productivity of both forage and seed yield when plants are self-fertilized. The decrease is very marked in most cases; for example, Williams (31) reports that 14 parent plants produced an average of 2,433 seed per plant, while the average yield of the first-generation selfed progeny was only 301 seeds. Kirk found that the first generation selfed produced only 62 percent as much as the cross-fertilized parent, and the second selfed generation only 30 percent as much as the original parents.

The German workers, including Dann (7), also found a decided decrease in seed production with self-fertilization as compared with cross-fertilization. Helmbold (14) found that crossing gave a higher percentage of pods than selfing. By crossing with foreign pollen, 24.86 percent of the flowers formed pods. With close pollination (pollen from the same plant but different flowers) 18.26 percent formed pods, and with strict selfing 17.54 percent formed pods. Crossing also gave the highest number of seeds per pod, an average of 2.34, while inbreeding gave the least, an average of 1.38 seeds per pod. Most workers agree that there is no self-sterility, in the true sense, in Medicago sativa or M. falcata.

Tysdal and Clark (27) found decided decreases of seed production in self-fertilized lines as a general rule, but point out several instances where selection for seed productivity increased production, particularly in Turkistan lines, which as a rule are naturally low in seed yield. These lines were carried into the fourth generation of selfing and represent a_decided improvement in the inherent ability to set seed over the original parent. Kirk (18) has isolated a strain of alfalfa during the course of his breeding work that he characterizes as “autogamous”, that is, it is extremely self-fertile and sets seed readily without manipulation.

The seed production resulting from hybridization compared to that of the original parental stock has not been so carefully worked out.  It is evident that open pollination or cross-pollination between selfed lines brings them up nearly to parity with the open-pollinated parents, but there are very few definite examples, if any, of large increases attributable to hybrid vigor. Most of the comparisons have been with the progeny of self-fertilized individuals and not with the original parent, and the relative improvement in the cross is therefore difficult to determine. Carlson (5) found decided decrease in seed production upon self-fertilization, and then when open pollination—with no way to determine the amount of crossing—was allowed, seed production increased over that of self-pollination but still did not reach that of the open-pollinated parents. In the work reported up to the present time 1t has not been: possible to recombine desirable inbred strains with the object of producing a superior first-generation hybrid, as is being done with corn, because such inbred strains were not available; but at present there are a number of lines that have superior germ plasm with respect to seed production as well as other desirable characters.

The available data on the influence of self-and cross-fertilization on forage production somewhat parallel those on seed production.  Kirk (16) found the following percentages of forage yields: Cross-fertilized, 100; first generation selfed, 81; second generation selfed, 72; third generation selfed, 53 (fig. 7); but he also found certain second- and third-generation selfed lines that produced 100 percent or more as compared with the original parent. This coincides in general with results of other workers, there being not such a very great decrease in forage production of some lines, and a tremendous variability with respect to the reaction of different lines—some showing great loss of vigor, while others show very much less. It must be admitted, however, that the chance of obtaining a superior forage-yielding strain of alfalfa by self-fertilization appears rather remote at the present time.

Figure 7.—A, Representative alfalfa plants from strain no. 22, showing reduction in vigor due to self-fertilizalion: a, Open-fertilized; b, first generation selfed; c, second generation selfed. B, Representative alfalfa plants from strain no. 3, showing reduction in vigor due to self-fertilization: a, Open-fertilized; b, first generation selfed; c, second generation selfed. (Courtesy of L. E. Kirk, Dominion Agrostologist, Ottawa, Canada.)

As in the case of seed production, most of the comparisons in forage production are between open- and self-pollinated lines. Waldron (29), however, as far back as 1920 pointed out hybrid vigor in crosses between two alfalfa species. He allowed natural crossing to take place between Medicago sativa and M. falcata. Subsequently he obtained yield data from the first-generation-hybrid individuals compared with other individuals produced by normal pollination within the species. He found an increase in forage yield of 51 percent of the M. sativa X the M. falcata hybrids over the pure M. sativa, and 43 percent increase of the M. falcata X M. sativa hybrids over the pure M. falcata.

The general results of inbreeding and crossing in alfalfa point to the strong possibility of hybrid vigor being obtained for forage yield if the proper combinations of lines are made. The results also point to the possibility of using species crosses to effect improvement. In a later paragraph more information is given on various species that may have possibilities for crossing.

In the replies from questionnaires sent to practically all alfalfa workers in the world in connection with this survey, many indicated that they were selecting for cold resistance and others that they were selecting for both cold and disease resistance. In the past Grimm alfalfa was an outstanding example of natural selection for cold resistance. The introduction of various lots of seed and subsequent selection and increase, as in the case of Cossack, Ladak, and other varieties, resulted in the production of additional material of high cold resistance.

In many projects selection is being carried on with the object of purifying strains and making them homozygous for certain characteristics, then recombining the lines to form new varieties.  Such work has advanced to the point where some information has been obtained on the breeding behavior of lines, but very little on the behavior of the recombinations.

   Inheritance has clearly played an important part and segregation into hardy and non-hardy lines is plainly indicated in the second generation of self-fertilization. Strains IV and VII may be cited as obvious cases in which lack of hardiness has been transmitted in some degree from one generation to another. In one second generation line of strain IV, every plant was winter killed. [The cross-fertilized parental stock of strain IV winter-killed 28 percent.] Lines III and XIII are notable illustrations of segregation in the second generation of selfing for hardy and non-hardy families of plants.
   In striking contrast to the strains in which inherent nonhardiness made an appearance are * * * strains * * * in which practically no winter-killing occurred.

A number of superior lines have been segregated by various workers in the United States. Wisconsin, Kansas, New Jersey, Michigan, and Nebraska have had rather intensive improvement programs underway, and progress is reported in fixing desirable characters such as cold and bacterial wilt resistance in certain lines. Peltier and Tysdal (23) report that selfing alfalfa through the fifth generation has increased the homozygosity for bacterial wilt resistance—that is, a larger and larger percentage of the plants were resistant—provided selection for this character was carried on during the inbreeding process. If no selection for disease resistance was practiced during the inbreeding process, a rather marked decrease in bacterial wilt resistance occurred from generation to generation, although some few lines were consistently high in bacterial wilt resistance. Practically the same results were obtained with cold resistance. Selfing without rigid selection for cold resistance and elimination of the cold-susceptible individuals resulted in a marked decrease in resistance, taking the population as a whole. There was, however, great variation and segregation in different lines, as has been found by other workers.  Thus, when the cold-resistant segregations were selected by means of artificially controlled freezing tests, the cold resistance of superior lines was maintained in spite of self-fertilization. It was also found possible to obtain high bacterial wilt and cold resistance either in the same lines or independently, thus indicating independent inheritance.  Figure 8 shows two hybrids relatively resistant to bacterial wilt, as compared with the bacterial wilt-susceptible Grimm variety.

Brink, Jones, and Albrecht (3) at the Wisconsin station report segregation for bacterial wilt resistance in selfed lines from Hardistan alfalfa, some having a very high degree of bacterial wilt resistance.  They state (3, p. 642): “Resistance to bacterial wilt in alfalfa behaves in inheritance as an intergrading character and probably rests upon a complex genetic basis. A factorial interpretation is at present “impossible.”

In certain crosses between resistant and susceptible lines the same workers found varying percentages of resistant offspring. In the case of a Turkistan X Hairy Peruvian cross, 58 percent of the second-generation offspring were resistant, while a Turkistan X Grimm cross gave relatively few resistant segregates.

Thus while complete success has not yet been attained in the fight against winter hazards and disease, it is safe to say that remarkable progress has been made in obtaining lines that are superior in these characters. These lines contain the necessary genetic stability for these characters, and the next step will be to combine them to produce a variety with as much bacterial wilt resistance as is now found in any commercial variety, or even more, together with such desirable characters as high forage and seed yield, freedom from leaf diseases, and other attributes. To say that this is an easy task is to underestimate the difficulty of the problem and the whims and caprices of nature.

In the alfalfa-improvement work, the Department of Agriculture is cooperating with a number of State stations, among which the work in Kansas, Wisconsin, and Nebraska has been longest in progress.  At each of these institutions superior strains are now available, some strains having more than twice the bacterial wilt resistance of the best commercial varieties. The Wisconsin station reports that among its most promising material are lines having very high cold resistance selected out of hardy varieties, and also some bacterial wilt resistance found in occasional plants from well-known and highly susceptible American varieties. The Kansas station has also reported increasing the bacterial resistance by selection in the Kansas Common strain.  The Nebraska station has promising lines developed from plant selections from old fields of the State, foreign introductions, and the Ladak and Cossack varieties.

The New Jersey station has had selection and hybridization in progress for some time and reports the possibility of selection for a type of root resistant to heaving, as well as selection for adaptation to particular soil conditions.

Various stations now also have access to strains with rhizomes or underground stems. These are particularly interesting from the standpoint of pasture types and erosion control, as they form a matted growth and bind the soil.

There is some division of opinion, but in the main considerable agreement, regarding the kinds of insects that assist seed setting in alfalfa.  Practically all workers agree that the leaf cutter bees (Megachile spp.) are very effective in causing tripping or forcing of the pistil out of the keel. Piper et al. (25) found the bumblebee (Bombus spp.) to also be fairly effective for tripping. They found that butterflies caused practically no tripping, and this was true also for moths and other night-flying insects. The ability of the honey bee (Apis mellifera L.) to trip alfalfa flowers is not so easily clarified. Piper et al. found that honey bees tripped only from 0.3 to 4.7 percent of the flowers visited and many visits to the flower were required before tripping was effected. Dwyer (9), of Australia, has found that honey bees cause a considerable amount of tripping and has suggested the use of honeybees in cages in breeding work. Michigan workers have also found the honey bee to be effective when confined to small areas. Helmbold (14) states that honey bees collecting pollen cause tripping and attributes more tripping to them than to bumblebees. He also says that the following bees are effective in tripping alfalfa flowers: Macropis labiata F. (female), Melitta leporina Panz., and Anthophora bimaculata Panz.

There is no doubt from the work of numerous investigators that insect visitation under most conditions will improve seed production, and it is probable that insects can be used to advantage for controlled pollination in certain breeding and improvement work.

There is some evidence that progress can be made in selecting lines resistant to harmful insects. Painter and Grandfield in Kansas have selected individual plants that are much more resistant to aphids (Illinoia pisi Kalt.) than the average of the variety. Some workers have also found individual plants that seem to carry resistance to leathoppers (Empoasca spp.). At present these represent only possibilities in superior germ plasm. Insects that harm alfalfa from the standpoint of seed production, upon which little or no selection for resistance has been done, include the clover seed chaleid (Bruchophagus gibbus Boh.), certain species of bugs of the genus Lygus, and Say’s stinkbug (Chlorochroa sayi Stal).

In June 1934 a meeting of 27 alfalfa workers from 7 States and the District of Columbia was held at Lincoln, Nebr., and at this meeting attention was given to the formation of an informal association for the benefit of all workers interested in alfalfa improvement. In order to get the reaction of the eastern men it was decided to call another meeting to be held in connection with the American Society of Agronomy meeting at Washington, D. C., in November 1934.  Nineteen States, the District of Columbia, and Canada were represented by 54 workers. After a thorough discussion a committee of five was appointed, composed of H. L. Westover, R. A. Brink, T. A. Kiesselbach, D. W. Robertson, and H. B. Sprague, to develop plans and methods for a permanent alfalfa improvement conference.  This committee called & meeting of all interested workers to be held in connection with the meeting of the Corn Belt section of the American Society of Agronomy at St. Paul, Minn., June 1935, at which time final organization of the conference took place. At this meeting, representing 15 States and the District of Columbia, with an attendance of 78 workers, the following motion was adopted:

That the guidance of the Alfalfa Improvement Conference be in the hands of an executive committee of five, consisting of H. L. Westover, permanent secretary, and four additional members, one of whom would be chairman, to be elected biennially at the conference to be held in conjunction with the Chicago meeting of the American Society of Agronomy; and that summer conferences be held in alternate years at an experiment station where alfalfa investigations are in progress, the time and place to be determined by the committee.

The following were elected as members of the executive committee to serve until the fall of 1937: R. A. Brink, chairman; T. A. Kiesselbach, H. B. Sprague, and D. W. Robertson. In Mr. Westover's absence on plant exploration trips, H. M. Tysdal has been acting secretary.

Since its inception and organization the Alfalfa Improvement Conference has been active in disseminating information on progress in alfalfa breeding, has taken an active interest in plans for seed increase of desirable improved strains under isolation, has assisted in the exchange of breeding material, and at the biennial summer meeting held at Madison, Wis., in June 1936, laid the foundation of a cooperative program of testing new strains. In this cooperative testing two types of nurseries will be used—(1), an “observation” nursery composed of duplicate rod rows with appropriate standard checks, and (2), an advanced nursery composed of perhaps five or six replications of multiple-row plots. Yields will be taken on the latter nurseries, and also, where possible, on the former.

It is planned to have a considerable number of observation nurseries scattered throughout the country so that experiment station workers will have an opportunity of testing out the available new strains for their own conditions, and this will enable them subsequently to make intelligent varietal recommendations to alfalfa growers of their own States. The advanced nurseries will be located in representative areas to test out any definite regional adaptations that are found in the improved strains. One or more tests are also contemplated in a recognized alfalfa seed producing section to test this character. In addition to these cooperative field tests, attempts will be made to include testing under controlled conditions for such characters as resistance to diseases, to insect pests, and to low temperatures.

The Alfalfa Improvement Conference has already proved itself to be a vital force in coordinating the alfalfa improvement work of the United States. Reports of the conferences already held may be obtained from the Division of Forage Crops and Diseases, Bureau of Plant Industry, United States Department of Agriculture, Washington D. C.

Even the most optimistic workers fail to see how it would be possible to produce one variety of alfalfa that would be the best for all sections of the country. Some workers, however, recognize a need for the development of strains of alfalfa especially suited to at least four general regions: (1) The northwestern region, north of the southern boundary of Nebraska and west of the eastern boundaries of North Dakota and South Dakota; (2) the northeastern region, which may roughly be designated as the area bounded on the west by the western boundaries of Minnesota and Iowa and on the south a line representing approximately the southern boundary of Pennsylvania; (3) in the middle region, including Kansas and Oklahoma and the surrounding territory eastward and westward; (4) the southwestern region, including southwestern Texas, southern New Mexico, Arizona, most of California, and the extreme southern parts of the United States along the Gulf of Mexico.

In regions 1 and 2 it is essential to have an alfalfa of high cold resistance. Bacterial wilt can also be found throughout these regions, it is severe only in those areas where moisture and other conditions are favorable; it is not serious as yet in the dry-land areas or in the eastern regions where short rotations are the rule. However, it causes severe damage in parts of Ohio, New Jersey, and other Eastern States.  The chief difference between the requirements for regions 1 and 2 relate to resistance to various leaf spots, particularly the leaf spot caused by Pseudopeziza medicaginis (Lib.) Sace. and leaf blotch (Pyrenopeziza medicaginis Fekl), and also to dormancy habits and resistance to potato leafhopper yellows. Cold-resistant Turkistan alfalfa has been fairly successful in region 1 but not in region 2, chiefly because of its susceptibility to leaf spots and the fact that in some cases its slow recovery after cutting allows grasses to encroach. At one experiment station in the Union of Soviet Socialist Republics, selections less susceptible to leaf spot have already been made, and it does not appear impossible that eventually a strain can be produced that will combine the qualities necessary for adaptability to both regions, 1 and 2. This would be all the more desirable because seed is often produced in the western area to be used in the eastern area. Also there is some evidence indicating an increase in the severity of bacterial wilt in eastern States, which would make bacterial wilt resistance desirable for this region.

In region 3, cold resistance is a less important factor, but it can by no means be entirely neglected. Bacterial wilt resistance is desirable if not necessary for many areas, and it seems probable that if a strain can be produced combining bacterial wilt resistance and the desirable habit of growth of Kansas Common alfalfa, it will be very well adapted for this region.

In region 4 the climate is so mild that cold resistance need not be considered, although there is apparently considerable difference in ability of the foliage of different strains to resist frost, and it is desirable to select for this character. Since tests have shown that the nonhardy alfalfas grow more rapidly and give better yields of hay in this region, selection work can be confined largely to southern types. Bacterial wilt has not been important in this region, although it has been found.  Fortunately certain Persian introductions of the nondormant type have shown some bacterial wilt resistance and these are available for selection and breeding work for the region.

It is apparent from the foregoing that a large amount of selection and recombination of characters must be accomplished before the desirable alfalfas are obtained. Fortunately much of the foundation stock, including lines of high resistance to certain diseases and to cold, is already available. A cooperative arrangement with the various States to give accurate information on the adaptation of all new strains produced is now available under the auspices of the Alfalfa Improvement Conference.

The ultimate objective will be the combination of as many desirable characters in a single individual strain as possible. Most plant breeders constantly bear in mind and guard against the possibility that selection for one character, such as bacterial wilt resistance, may actually lead to the development or retention of characters undesirable in other respects. For example, bacterial wilt resistance can readily be obtained in Turkistan lines, but the strain is still undesirable because of other characters, including high susceptibility to leaf diseases.

Naturally present-day alfalfa breeders use a wide variety of methods in attacking the problem of improvement, although the underlying principles are the same. In hybridization work where emasculation is desired most American workers use the suction method or a combination of suction with a jet of water directed on the stigma. The suction method operates on the principle of a vacuum cleaner and is illustrated in figure 9.

Figure 9.—Emasculation of alfalfa flowers by suction. The glass tube is held over the stigma and stamens, and the suction (in this instance supplied by a rubber tube connected to the intake manifold of an automobile) removes the anthers and pollen.  If all the pollen is not removed, a jet of water is applied to the stigma and suction finally removes all trace of pollen.

It has been found advantageous not to allow the stigma to strike the standard or any other object when it is tripped or forced out of the keel for emasculation. It has also been found that in general it is unnecessary to emasculate the flower at a very early stage; emasculation is usually delayed until full bloom, even though the anthers have become ripe. If the pollen is carefully removed, apparently there is little danger of self-fertilization, and foreign pollen can then be applied immediately.

Selfing is accomplished by the use of bags, screen cages, or screened greenhouses, the flowers usually being artificially tripped, although not always. Some strains have been produced that set seed without any manipulation of the flower. Figures 10, 11, and 12 show some of the ways in which the problem of seed increase of selected lines is being met.

Figure 10.—Increase of seed of selected lines of alfalfa in the greenhouse at the Nebraska Agricultural Experiment Station. The greenhouse is screened against insects, and the flowers are tripped by hand, insuring self-pollination. Good seed setting can usually be obtained in the greenhouse even in unfavorable seasons, although temperatures often reach 120° F. inside.


Figure 11.—Seed increase of a selected alfalfa strain in an isolated block. Such a plot must be separated from any other by at least 20 rods; in this case the separation was about a quarter of a mile. The plants were transplanted to irrigated land in western Nebraska in the spring of 1936 from seedlings started at the United States Yuma Field Station, Bard, Calif., in December 1935. These plants produced a fair amount of seed the first year. The plot is surrounded by corn and sugar beets.


Figure 12.—Small, portable thresher for threshing both single plants and increase blocks of alfalfa. The single-plant material is run only over the rubber drum with apron shown at the right, while larger quantities are put through the cylinder, and pods that are not threshed fall through the screen and are then run over the rubber drum, which rubs all the seed out. The rubber drum is powered through an automobile transmission so the drum can be stopped when not in use, even though the cylinder is going. The whole machine is mounted on the chassis of a car, and the motor of the car used as power. This thresher has proved very satisfactory for relatively small lots.

Perhaps of greater interest than details of technique are the principles followed in the breeding program itself. Some workers allow open-fertilization in the nursery and select the best individual lines for propagation, while others employ strict inbreeding methods with the object of more rapidly fixing the characters desired and then recombining if necessary. Still others use a combination of these methods.  Without doubt many alfalfa breeders are using the same method that has produced such remarkable results in hybrid corn, as described by Merle T. Jenkins in the 1936 Yearbook of Agriculture.

The problem of how to determine which lines when crossed will produce a superior hybrid is of great interest to alfalfa workers. At present the only way to find out is to try the lines in actual crosses, and it is difficult to make as many crosses as are necessary to test all combinations. Corn workers use the top-cross method rather extensively at the present time for eliminating undesirable strains, and it has been suggested that a modified application of the same principle may be useful in alfalfa.

Evidence seems to indicate that long-continued inbreeding is not necessary to fix desired characters sufficiently for practical breeding purposes. If this is true a great deal of labor and time will be saved and also a larger number of lines can be produced and tested.

The backcross method or its modifications, as, for example, Richey’s "convergent improvement" method, is apparently not very much used with alfalfa. Some type of backcross may be useful in such a problem as combining the bacterial wilt resistance of Turkistan selections with the desirable characters of Grimm, Cossack, or Hardigan.  The application of the backcross method is not simple when the inheritance of resistance is complex, as is apparently the case with bacterial wilt, but the method should not be overlooked when it is yielding results in various other crops.

To obtain further information on the present status of alfalfa improvement, questionnaires were sent to all experiment stations in the United States and all foreign workers of whom there was a record.  Among 40 replies, 23, representing opinions from England, Germany, Australia, and Canada, as well as the United States, indicated that alfalfa breeding or improvement work was in progress. In the replies to the question “What are the objectives in your selection or hybridization work?” the following objectives were mentioned the number of times shown:

It is interesting to compare these replies with those obtained in 1934, given in the supplement to the Report of the Second Alfalfa Improvement Conference. The most significant change is found in the increased number of workers at present interested in selection for a pasture type of alfalfa for grazing, and also the increased number interested in selection for soil adaptation. This undoubtedly indicates a trend toward the increased use of alfalfa for grazing and a desire to use it on land to which it is at present not well adapted.

1. Technique in methods of hybridization
2. The mode of inheritance of various characters
3. Hybrid vigor, including interspecies crosses
4. Factors affecting seed setting in alfalfa
5. Fundamental research on the nature and control of various diseases
6. The mosaic problem
7. Effective means of isolating pure seed for increase
8. Interregional testing, including hardiness and disease tests
9. Production of improved seed
10. The use of the backcross method, or modifications, in alfalfa breeding

THERE is rather a large amount of literature dealing with the general genetic behavior of alfalfa, but very little has been done on the inheritance of any given character. This is to be expected in a crop worked with as little as alfalfa, but nevertheless it is a handicap to the plant breeder in many respects. As self-fertilized strains having a known inheritance are developed, more information of this kind should be forthcoming.

Most of the work so far has involved crosses between the two contrasting species, Medicago sativa X M. falcata. In such a cross Korohoda (20) has reported on the inheritance of flower color, shape of leaves, and structure of the stem. With regard to the inheritance of flower color in the purple X yellow cross, he states that the former supposition that two or three hereditary factors were involved was found to be inadequate. The results of his studies indicated at least four factors, one for each fundamental coloration—cream, blue, and violet—and one or two that intensify these colors.

With respect to the shape of the leaves of the hybrid, the shape typical of Medicago sativa was observed in the second generation in 28 plants, that typical of M. falcata in 196 plants, and an intermediate in 424 plants. It was not found possible to calculate the relations, assuming the existence of two, three, or four factors.

When examining the structure of the stem in the second generation, stems of the type of M. falcata were observed in 565 individuals, and of the type of M. sativa in 30 individuals. Since the ratio of these numbers (18:1) is close to 15:1, the workers assumed the existence of two hereditary factors, with the falcata type dominant over the sativa type.

MacVicar (22) reports the results of an investigation to determine the inheritance of black and white seed coat characters in alfalfa and whether or not the former could be utilized in breeding as a marker for identifying improved strains. He says:

   The available evidence indicated that the white seeded parent was homozygous for a recessive factor which results in the absence of yellow pigment, and that the inheritance of this character was comparatively simple. Inheritance of the black seeded character, on the other hand, was fairly complex, requiring the assumption of at least three factor pairs. The original black seeded plant was thought to have arisen as a single gene mutation. This gene, primarily responsible for pigmentation of the seed coat, together with at least two modifying factors was postulated as the most probable genetic factorial basis to account for the breeding behavior of the original black seeded parent.
   It was concluded that the character of black-seededness would be valueless from a utility standpoint.

The cytological aspects of alfalfa have also been neglected until recently, when several interesting papers have been published.  Among these is a paper by Fryer (12), summarizing much of what is known regarding chromosome numbers in Medicago species, and another by Cooper (6) on embryology, reporting the important fact that according to his observations the lack of seed production in various plants seems to be due not to lack of pollination or fertilization but to failure of the ovule to develop after it has been fertilized.  In plants that fail to set seed after effective pollination takes place, the young embryos abort. Direct evidence regarding the cause of the abortion was not available, but it was believed to be an unbalanced nutritional condition.

THE following list includes mainly the breeders and workers employed by institutions that returned questionnaires on superior germ plasm in alfalfa. Nearly all the workers listed as State agricultural experiment station employees devote only a small part of their time to alfalfa-breeding investigations. The remainder of their time is given to investigations on other crops. This is also true of some of the field staff of the Division of Forage Crops and Diseases, Bureau of Plant Industry, United States Department of Agriculture. Early workers are listed on page 1233 [This appears to be some typo, but I cannot find where this list is- ASC]. The names of alfalfa breeders listed for foreign countries were all given in the returned questionnaires.
An asterisk (*) denotes United States Department of Agriculture employee.

United States Department of Agriculture, Bureau of Plant Industry, Division of Forage Crops and Diseases, Washington, D. C.: H. L. Westover.*
California Agricultural Experiment Station, Davis: B. A. Madson, F. N. Briggs
Colorado Agricultural Experiment Station, Fort Collins: D. W. Robertson, R. M. Weihing.
Kansas Agricultural Experiment Station, Manhattan: C. O. Grandfield.*
Kentucky Agricultural Experiment Station, Lexington: E. N. Fergus.
Michigan Agricultural Experiment Station, East Lansing: E. E. Down, S. T. Dexter, H. M. Brown.
Minnesota Agricultural Experiment Station, St. Paul: A. C. Arny.
Montana Agricultural Experiment Station, Havre: M. A. Bell.
Nebraska Agricultural Experiment Station, Lincoln: T. A. Kiesselbach, H. M. Tysdal.*
New Jersey Agricultural Experiment Station, New Brunswick: H. B. Sprague, E. M. Hodges.
New Mexico Agricultural Experiment Station, State College: J. C. Overpeck, G. N. Stroman.
New York Agricultural Experiment Station, Ithaca: C. H. Meyers.
Rhode Island Agricultural Experiment Station, Kingston: T. E. Odland, H.F.A. North.
Utah Agricultural Experiment Station, Logan: R. J. Evans, B. L. Richards, J. W. Carlson.*
Wisconsin Agricultural Experiment Station, Madison: R. A. Brink, A. H. Wright, O.S. Aamodt, E. J. Delwiche (Green Bay), A. L. Bibby (Spooner), A. M. Strommen (Spooner), L. E. Muskavitch (Ashland), F. R. Jones.*

Dominion of Canada Experimental Farms, Ottawa, Ontario. L. E. Kirk, J. M. Armstrong.
University of Saskatchewan, Saskatoon, Saskatchewan: T. M. Stevenson, William J. White.
University of Alberta, Edmonton, Alberta: J. R. Fryer.
Ontario Agricultural College, Guelph, Ontario: R. Keegan, O. McConkey.
McGill University, MacDonald College, Quebec: J. N. Bird.

Bathurst Experimental Farm, Bathurst: W. T. Atkinson.
Grafton Experimental Farm, Grafton: W. H. Darragh.
Riverina Experimental Farm, Yanco: W. H. Poggendorff.
Hawkesbury Agricultural College, Richmond: N. S. Shirlow.

Welsh Plant Breeding Station, Aberystwyth: R. D. Williams.

Kaiser Wilhelm Institute, Munchberg: J. Hackbarth, Dr. Schrock.

Sveriges Utsädesforening, Svalof: N. Sylven, O. Holmgren.
Sveriges Utsädesforening, Ultuna: R. Torssell.

Medicago platycarpa is a low-growing perennial with large broad leaflets, yellow flowers, and large flat pods, found mainly in Siberia. According to Hansen its distribution is mainly along the edges of timberland and in open places in the native timber, indicating that it might be adapted to sheltered regions such as the timber sections of northern Minnesota and Wisconsin and westward into the Rocky Mountains.

M. ruthenica is a small semierect perennial with small narrow leaflets, yellow flowers, and small pods. Hansen found this species growing wild in a section of the Gobi Desert in nearly pure sand. In general it is found scattered in dry, stony soils. As a fodder plant this species is greatly relished by the cattle, horses, sheep, and camels kept by the Mongolian nomads. Its distribution is farther north than that of Common alfalfa (M. sativa).

M. arborea is the largest representative of the Medicago genus, attaining a height of upward of 10 feet. It is a native of the Mediterranean region of Europe and does not thrive in cold climates. It is cultivated to a limited extent in various portions of its range, but as it gets woody too quickly and is less productive than M. sativa, that species is much more in favor.

M. falcata is an upright to prostrate perennial with small elongated leaflets, yellow flowers, and falcate pods; It is distributed over a wide range in eastern Europe and western Asia. Apparently it combines readily with M. sativa to form many of the cultivated varieties such as Grimm and Cossack, which are classified as M. media in the foregoing key. Many strains, though not all, are very cold-resistant, and certain types also endure pasturing rather well. It is now being used in breeding programs to a considerable extent.
   A point of particular interest has recently been raised by Fryer (12), who found different chromosome numbers in M. falcata. In two strains he found the number to be 2n=32, while in another strain he found it to be 2n=16. It is probable these two types would react differently in crosses.

M. gaetula is particularly noted for its rhizomes, by means of which it spreads readily like sod-forming grasses. It isnow being used in crosses to produce pasture and soil-binding types.

M. glutinosa is a native of the Caucasus Mountains and Trans-Caucasia generally, especially of Armenia, where it is found up to an elevation of 7,500 feet.  It is found growing in a very dry upland region and is more vigorous than most Medicago species of Caucasia.

M. hemicycla is found in the Caucasian region and is somewhat similar in morphological type to M. media.  It is considered to be a natural cross between M. sativa and M. falcata.

M. coronata is remarkable on account of its very high drought resistance. It is an annual found in all parts of Palestine, but its occurrence on the mountain slopes is particularly interesting, as the soil there is only an inch or two deep over the rocks. The seed setting of this variety is also high.

McKee and Ricker (21) state that the nonperennial species of Medicago consist principally of bur-clovers, mostly annual plants native to the Mediterranean region. Spotted bur-clover (M. arabica), California bur-clover (M. hispida), and black medic (M. lupulina) are the only species now widely distributed in the United States. The feeding value of bur-clovers, both those with and those without spines, is good. Among the latter the three most promising are M. confinis, M. orbicularis, and M. arabica inermis.