[starts on page 738 of the 1937 USDA Yearbook in the Stone Fruits chapter -ASC]


APRICOTS

THE apricot is prized by all who like the stone fruits, and when eaten fresh it is considered by many to be the most delectable of this group. Unfortunately, however, very few apricots are grown for fresh fruit in the States east of the Rocky Mountains, and most people know the flavor of this fruit only from the canned or dried product. Its production is restricted to a relatively small area in this country where climatic conditions are favorable. Most varieties can withstand winter cold as well as peaches, but the blossom buds develop rapidly under favorable growing temperatures in late winter after the rest period is over, and the crops are frequently lost from late freezes and spring frosts.

The commercial production of the apricot (fig. 21) is confined largely to the Pacific Coast and Intermountain States (5, 20). California leads with a potential average production considerably in excess of 200,000 tons. Of the average crop of 266,000 tons harvested during the years 1931-33, approximately 76 percent was dried, slightly over 14 percent canned, and about 10 percent was shipped or consumed locally as fresh fruit. Because of the great perishability of this fruit and the need for quick handling, fresh apricots are on the market in the Eastern States for only a short time and their distribution is limited to large centers of population.

BOTANY AND HISTORY OF THE APRICOT

All of the important commercial varieties of apricot. grown in this country today belong to the species Prunus armeniaca L. The name of the species, like that of the peach, is a geographical misnomer. The apricot was formerly considered a native of the Caucasus and Armenia, but later studies suggest that China is its native home. It is said that Alexander the Great brought the apricot from Armenia to Greece, whence it was taken to Italy. The Romans cultivated this fruit, and it is described in the writings of Pliny and Dioscorides. It was later carried to France, and there is mention of its being in England in Turner’s Herbal, published in 1562. The fruit is now cultivated in all of central and southeastern Asia, and in parts of southern Europe and northern Africa. There seems to be no mention of it in the United States until 1720, when it was said to be growing abundantly in Virginia. It was doubtless among the fruits brought into southern California early in the eighteenth century by the Mission Fathers. Its culture spread to the valleys farther north, where climatic conditions were more congenial. Wickson (33) reports that Vancouver found a fine orchard of fruits, including apricot, at Santa Clara in 1792. In 1935, 17 varieties were described as growing in England. Downing (12, pp. 236-242) names 26 varieties, and the American Pomological Society (1) lists 11 varieties as growing in the United States in 1879.

In tree, fruit, and flower characters the apricot seems to be somewhat intermediate between the plum and the peach. The trees are large and spreading, and in this respect are more like the peach and some of the Japanese plums. The leaves are broad, heart-shaped, dark green in color, and held erect on the twigs. The flowers are white, resembling those of the plum in color, but are borne not in clusters but singly or doubly at a node on very short stems. Like the peach, the apricot is self-fruitful and will set fruit when its blossoms are selfed. The pit is smooth, somewhat like that of the plum, but broader, somewhat flatter, and more winged. The fruit is nearly smooth, round to oblong, in some varieties somewhat flattened, and in general rather more like the peach in shape. The flesh is typically an attractive yellow to yellowish orange. The kernels of some varieties are sweet.


Figure 21.—Peach and apricot growing constitutes an important industry in California, The apricot trees, in the immediate foreground, and the peach trees in the rear are a part of a large orchard with rows 3 miles long.

The peach, plum, and apricot may be readily intergrafted. The apricot does well on peach stock, but the peach on apricot stock is not entirely satisfactory.

In addition to the common apricot (Prunus armeniaca), which comprises all of the commercial varieties grown in this country, several other species are of interest to the breeder. The black apricot (P. dasycarpa Ehrh.) has fruits of small size, dark purple or black in color, and for the most part of inferior quality. The trees more closely resemble the plum and possess considerable hardiness in wood and bud.

The Japanese apricot (P. mume Sieb. and Zucc.) is noted principally for the ornamental character of the trees. The flowers and fruits also are very attractive.

Types native in other countries have been described as species but are classed by some authorities as subspecies. The Russian apricot (P. sibirica L.). is possibly a strain of the common apricot (P. armeniaca). Trees of the Russian apricot differ from the common apricot in bearing smaller fruit of poorer quality. They are considered very much hardier in their native home, but certain strains brought into this country have not shown superior hardiness under test. The trees have a characteristic upright growth habit, are thickly branched, and possess more thornlike spurs. The small fruits set in clusters.

Another probable subspecies, the Manchurian apricot (P. mandschurica Koehne), is a common wild tree in central Chosen. Its fruit is similar to that of the common apricot, but the leaves differ, and its bark is thick and corky. This subspecies may be a selected strain of the common apricot.

The apricot is widely distributed throughout Asia, and a large number of seedlings have been observed growing wild in various localities. In China some travelers report the apricot only as a cultivated tree, but others have found it growing wild in the northern Provinces.

BREEDING MATERIAL

The apricot is less rich than some of the other stone fruits in species and horticultural varieties suitable for breeding material. The raw material consists of many old varieties introduced from England and France. Among those recognized as of English origin are Blenheim, Early Moorpark, Moorpark, and Hemskirke. These are all varieties, of high quality, with the Blenheim maintaining first importance as a commercial variety. Varieties of French origin are Peach, Oullins Early, Montgamet, Luizet, and Royal. Royal is the most important commercial variety of this group. ['Royal' and 'Blenheim' are actually the same cultivar, but came from two distinct introductions. -ASC] Like the English varieties, all the French varieties have certain commercial limitations. There is an excellent opportunity for the apricot breeder to combine their desirable characters by cross breeding. Work of this kind is already under way at State and Federal agricultural experiment stations, as will be pointed out later.

A large number of varieties have been introduced from the Union of Soviet Socialist Republics, many of these by J. L. Budd, of Iowa. As a class they are more hardy in bud, later in blossoming, with fruit of smaller size and poorer quality, but they are very productive. Some of the more important varieties of this group are Alexander, Budd, Gibb, Shense (Acme), Superb, and Toyahvale. Little work has been done in combining the qualities of these hardy sorts, which some botanists consider a separate species (Prunus sibirica), with the commonly grown varieties from western Europe.

In the last half century a number of promising seedlings and strains of American origin have been selected, but only the Tilton ranks with the older European sorts as an important commercial variety. As might be expected, most of the American varieties originated in Pacific Coast States. Among the more important are Newcastle, Alameda Hemskirke, Routier Peach, Derby Royal, and Sparks Mammoth, from California. Other varieties of more recent origin are Wenatchee Moorpark, which has been reported to be similar to if not identical with Moorpark, Riland, Gilbert, and Sofia, originating in the State of Washington. Among other older American varieties are Early Golden and Superb.

.

The apricot has been crossed with varieties of plum, particularly the Japanese plum. Luther Burbank produced a number of seedlings by crossing the apricot with this plum. Some of the more promising of these have been introduced under the group name plumcot. Among the more important are Apex, Corona, Rutland, Silver, and Triumph.

The crosses of apricot with plum have apparently been more successful than those with peach. No horticulturally satisfactory peach-apricot varieties have been reported.

OBJECTIVES IN APRICOT BREEDING

If apricot culture is to be extended beyond the present restricted areas where climatic conditions are favorable, varieties must be developed that are later in flowering in spring. From material that has been brought into this country, differences in bud hardiness and in blooming have been observed. There is need for the introduction of varieties from countries where apricots are growing and surviving temperatures as low as those obtaining during the winter months in this country. Many of these will doubtless prove worthless from the standpoint of edible fruit quality, but will serve as breeding material for the development of better varieties. In California considerable loss results from the dropping of blossom buds of certain varieties. Varieties that have a short rest period, are needed for those sections of the country where the winter temperatures are not low. Better canning, drying, and shipping varieties are also in demand. Evidence at hand would indicate that the commercial quality of varieties can be improved by breeding.

There is little information about the development of varieties by private breeders. A number of chance seedlings have been discovered by individuals, but it does not appear that any conscious attempt to select or breed new varieties has been carried on to the extent that it has with the other stone fruits. It is likely that many who were interested in better varieties were discouraged in their attempts because the parent material available for crossing was in itself not sufficiently hardy.

In the selection of material for breeding, difficulty may be encountered in establishing the trueness to name of varieties, since the same variety may be grown in two or more localities under different names. Some of the varieties representing desirable types are Moorpark, Royal, Blenheim, Tilton, Montgamet, and some selections of Russian and Japanese origin. For breeding studies in the eastern United States, where hardiness is an important factor, varieties should be used that have been tested and have demonstrated superior hardiness, such as strains of Russian varieties introduced by Budd, and more recent importations made by Hansen, of South Dakota, and_ the Division of Plant Exploration and Introduction, Bureau of Plant Industry, United States Department of Agriculture.

APRICOT BREEDING AT STATE AND FEDERAL STATIONS

Apricot breeding was started at the New York (State) Agricultural Experiment Station in 1922. Eighteen varieties, one seedling, and two P. I. numbered seedlings have been used. Eighty-four seedlings derived from definite crosses, 1,424 from open cross-pollination, and 9 from self-pollination have been set in the orchard for fruiting. Varieties used most extensively have been href="../BC/Apricots1900.htm#Alexis">Alexis & times, Doty (a local seedling) 15, Downing (late blooming) 5, Montgamet 6, Oullins Early 13, St. Ambrose 5, and Toyahvale 5. A seedling grown from a seed imported by the Department of Agriculture as P. I. 34265 has been considered worthy of a name. This variety was temporarily called “Frascati", as the seed was thought to have been imported from the vicinity of Frascati, Italy, but more recently it has been given the name Geneva.

At the North Dakota station apricot breeding work was started in 1924 in an attempt to develop varieties of sufficient hardiness to stand the winters of the northern Great Plains area. Over 2,000 seedlings are being grown and studied for their hardiness and quality of fruit.

At the South Dakota station, N. E. Hansen has been propagating trees from seeds collected by him in northern Manchuria in 1924. The fruits were taken from trees growing in localities reported to have minimum temperatures of —47° F. Twenty-three selections, called the Manchu group, have been propagated for test. Additional collections made in 1934 in eastern Siberia for propagation at Brookings are expected to give seedlings with greater hardiness than the Manchu.

Breeding work at the California station at Davis, Calif., was started in 1930. The objective is the development. of varieties of high quality suitable for shipping as fresh fruits, canning, and drying, but lacking some of the faults of the old varieties now grown commercially. Varieties used as pollen and seed parents have been Tilton, Royal, Hemskirke, Blenheim, St. Ambroise, Peach, Newcastle, Moorpark, Oullins Early, and in addition strains of Moorpark and Hemskirke. In the seasons of 1933 and 1934, one seedling each was obtained from the following interspecies crosses: Royal X Prunus pseudocerasus, P. mume X Royal, Pringle Late X Rutland plumcot, Diamond Jubilee nectarine X Royal, and Lovell peach X Royal. From the crosses made during 1930-35 there are at the present time over 2,000 seedlings growing in the orchard.

This material should provide a sufficiently large progeny for genetic studies of the varieties used as parents and serve as a source of superior seedlings that may be worthy of naming. A list of the crosses and the number of seedlings in each cross, as well as a list of varieties now being grown, is given in the appendix to this section.

At Palo Alto, Calif., apricot breeding by the United States Department of Agriculture in cooperation with Leland Stanford Junior University has been in progress since 1922. A search for varieties of high quality that would prove more satisfactory for the established apricot districts has been the main objective of this work. About 60 promising hybrids have been selected for further studying and testing. The more common varieties, such as Blenheim, Tilton, Moorpark, Royal, Newcastle, and Hemskirke, have been used as seed and pollen parents, and in addition the less common varieties Bergetti, Montgamet, McKinley, Luizet, Bremner, and Sparks. Hybrids of these varieties have been recrossed, and other combinations have been made by using promising parents introduced from southern Europe, Africa, and Asia in an effort to obtain certain desirable characteristics in the progeny. In this material from abroad are included Giallo di Tortona, Baas seedlings, Japanese seedling 26018, Sardinian, P. I. 28954, and P. I. 34272.

A list of the hybrids selected with the parentage and the years the crosses were made is given in the appendix.

APRICOT BREEDING IN OTHER COUNTRIES

A program of apricot breeding has been under way for some time under the supervision of the Department of Agriculture at the Yanco Experiment Farm, Sydney, New South Wales. The work has for its object the production of superior canning varieties, particularly later varieties than Trevatt, to extend the season and thus close the gap of ripening between the latest canning apricots and the earliest canning peaches. Importations of seed have been made from Palestine, Iraq, Syria, and Morocco, and from this material seedlings are now being grown. The varieties used in the crosses and for open pollination are Alsace, Bouche Peche, Mansfield, Moorpark, Lossie Blenheim, Tilton, Campbellfield, Bathurst, Trevatt, Newcastle, and Rose de Vaucluse. From results obtained to date, Moorpark seems to be the best parent variety for giving a useful range of seedlings, while Trevatt crossbred seedlings have better general quality. A Moorpark X Bouche Peche seedling is being propagated for orchard trial.

In Morocco, work is being carried on at the new State station at Ain Taoujdat, especially designed for research in horticultural genetics. New varieties of high quality are being sought for by hybridization. Ten distinct forms of native apricot (mechmech) have been studied comparatively since 1934 for their value as-stocks. Superiority has been shown by E. F. 136, 137, and 139.


GENETIC AND CYTOLOGICAL STUDIES WITH Apricots

There is little published information dealing with the genetics of hybrid progenies of apricot varieties and species.

Cytological studies have been made at the agricultural experiment stations of New York and California, and all apricot varieties examined thus far have 16 as the diploid (2n) number of chromosomes, which is the number found in sweet cherry, peach, and some species of plum. At the New York (State) Agricultural Experiment Station, chromosome numbers in exceptionally vigorous seedlings and also in abnormal seedlings from embryo cultures have been counted, but in a total of about 50 cases no deviation from the regular diploid type was found. Unsuccessful attempts have been made to induce polyploidy by selecting giant pollen grains under the microscope, mounting them on hairs, and applying them to the stigmas of flowers. Radiation experiments with stem meristem have also failed. This work is being continued, and other methods to induce polyploidy in apricots are being tried.

Cytological investigations are under way at the California station to determine the true hybridity of the plumcots. This is important in breeding work, to determine whether the characters in segregation will behave as true hybrids or whether they will behave separately as plums or apricots.

APPENDIX (APRICOT)

Table 9.—Locations of apricot-breeding work and names of workers in the United States and other countries
State or country, and institutionLocationWorkers actively engaged
California:
Agricultural Experiment StationDavisW.P. Tufts, E. C. Hughes
U.S. Department of AgricultureDavisJ.R. King
ditto
Palo AltoW.F. Wight
New York:  Agricultural Experiment StationGenevaR. Wellington, Olav Einset
North Dakota:
Agricultural Experiment StationFargoA. F. Yeager
U.S. Department of AgricultureMandanW. P. Baird
South Dakota: Agricultural Experiment StationBrookingsN. E. Hansen
Utah: Agricultural Experiment StationLoganF.M. Coe
New South Wales: Department of AgricultureSydneyH. Wenholz
Morocco: Experimental LaboratoryAin TaoujdatCh. Miedzyrzechi

Table 10.—Apricot seedlings growing at the California Agricultural Experiment Station, Davis, Calif.*
Year of crossNumber Seedlings plantedParents
193172Tilton X Moorpark
574Royal X Newcastle
104Royal X Hemskirke
226Royal X Moorpark
230Royal X Tilton
31Wenatchee Moorpark x Tilton
2Wenatchee Moorpark X Royal
21Hemskirke X Tilton
5Hemskirke X Moorpark
149Hersey Moorpark X Royal
33Blenheim X self
7St. Ambroise X Royal
93St. Ambroise X Tilton
172St. Ambroise X Moorpark
193213Royal X Peach
10Royal X Wenatchee Moorpark
185Royal X Oullins Early
25Royal X Alameda Hemskirke
57Royal X Grace
8St. Ambroise X Tilton
22St. Ambroise & Moorpark
8Peach x P.I. 38281
4Peach X Tilton
43Wenatchee Moorpark x Oullins Early
1Derby X Alameda Hemskirke
19332Newcastle x Peach
1Tree (22-1) X Peach
1Royal X Prunus psendocerasus
1Prunus mume X Royal
19341Pringle Late X Rutland plumcot
1Diamond Jubilee nectarine X Royal
1Lovell peach X Royal
* Verification of the nomenclature used in this and the following lists has not been possible in all cases, Where doubt exists as to the identity of a variety referred to by a name of uncertain validity, no attempt has been made to bring such name into conformity with the code of nomenclature, as it might later result in confusion.


Apricot-Breeding Material at the California Agricultural Experiment Station, Davis, Calif.
Prunus armeniaca:
   Alameda Hemskirke, Alexander, href="../BC/Apricots1900.htm#Alexis">Alexis, Bairam Ali, Barry, Beaugé, Bizant, Blackmon, Blenheim, Blush, Bolton, Boulbon, Brady, Breda, Di Breda, Budd, Early Cluster, Burtons Royal Seedling, Early Golden, B. W. Marshall, Early May, Catharine, Garlach, Royal, Chinese, Giallo di Tortona, Cluster, Gibb, Colorado, Gilbert, Cream, Great Plains, Crisomelo, Giffin Choice, Cutler, Derby Royal, Grosse Pêche, Gross Blanca Precoce, Particolare, Stephens, Harris, Paviot, Stewart, Hemskirke, Peach, Sugar, Hersey Moorpark, P. I. 20072, Superb, Janet, P. I. 28960, Tentazione, Jones, P. I. 34265, Thissell, Kaleden, P. I. 34270, Thompson Early, Knobel Blenheim, P. I. 38281, Tilton, Lampasas, Pringle, Toyahvale, Large Early Montgamet, Pringle Late, Trevatt, Red Beauty, Upham No. 1, Upham No. 3, Lewis, Riland, Losse Blenheim, Rivers, Wenatchee Moorpark, Lowe, Rivers Early, Wiggin, Luizet, Routier Peach, Wilson, Mammoth White, Zuccherino di Holub, Maxson, McKinley, Meyer Giant, Miner, Mognaga, Montgamet, Murgab, Nellie, Newcastle, New Large Early, Nicholas, Noble, Oullins Early, Rualt, Santa Fe, Sardinian, Sharpe, Shense (Casaba, Acme, Yakimene), Sloan, Smyrna, Snowball, Sophia, Sparks Mammoth, St. Ambroise, Stella, Prunus armeniaca var. ansu Maxim.:   Apricot Plum
Prunus dasycarpa:
    Black, Florizan, Prunus dasycarpa No.13
Prunus mume:
   Bongoume, Double Flowering, Japanese (P. I. 45523)
Prunus brigantiaca Vill.
Prunus sibirica


Apricot Hybrids Produced and Under Test at Palo Alto, Calif., in Cooperation Between the United States Department of Agriculture and Leland Stanford Junior University**
Year
Parents of hybrids
1923Bergetti X Montgamet
1931(Bergetti x Montgamet 30-371) X (Blenheim X Tilton 27-50)
1934(Bergetti X Montgamet 30-36) X Bremner
1932(Bergetti X Montgamet 30-36) X (Moorpark X Blenheim 28-52)
1923Blenheim X McKinley
1935(Blenheim X McKinley 27-21) X (Blenheim X Moorpark 12-58)
1920Blenheim X Moorpark
1932(Blenheim X Moorpark 12-55) X Japanese seedling 26-19
1932(Blenheim X Moorpark 12-59) X (Sparks X Blenheim 37-60)
1935(Blenheim X Moorpark 12-58) X 75222 Tunis 27-70
1935Blenheim X (Sardinian X Royal 37-56)
1923Blenheim X Tilton
1934(Blenheim X Tilton 27-50) X (Bergetti x Montgamet 30-35)
1933(Blenheim X Tilton 28-6) X (Blenheim X Moorpark 12-59)
1934(Blenheim X Tilton 27-50) X (Blenheim X Tilton 28-6)
1934(Blenheim X Tilton 28-7) X (Blenheim X 28954 13-26)
1932(Blenheim X Tilton 27-47) X Bremner
1931(Blenheim X Tilton) Hemskirke
1935(Blenheim X Tilton 28-6) X Japanese seedling 26-18
1932(Blenheim X Tilton 27-50) X (Moorpark Blenheim 28-52)
1932(Blenheim X Tilton 28-6) X (Sparks X Blenheim 37-60)
1933(Blenheim X Tilton 28-7) X (Blenheim X Tilton 27-50)
1934(Blenheim X Tilton 27-50) X (34272T2 X Blenheim 12-51)
1921Blenheim X 28954
1934Bremner 9-27 X (Blenheim X 28954 13-26)
1933Cirio 18-5A X (Blenheim X Moorpark 12-59)
1924“Crow apricot seedling"
1920Prunus dasycarpa X Blenheim
1927Giallo di Tortona X Moorpark
1932Giallo di Fortona X (Moorpark 9-16 X Japanese)
1933Hemskirke X (Blenheim X Tilton 27-50)
1935Japanese seedling*** 26-18 open 27-34C X (Blenheim X Moorpark 12-58)
1935Japanese seedling 26-18 X (Sardinian X Blenheim">Royal 37-56)
1923Luizet X Moorpark
1931(Luizet X Moorpark 28-39) X Blenheim
1923Moorpark X Blenheim
1931(Moorpark X Blenheim 28-52) X (Blenheim X Moorpark 12-56)
1932(Moorpark X Blenheim 28-42) X (Blenheim X Tilton 28-6)
1935(Moorpark X Blenheim 28-52) X (Sardinian X Blenheim">Royal 2-25 37-56)
1923Moorpark X Tilton
1931(Moorpark X Tilton 28-13) X Hemskirke
1933(Moorpark X_ Tilton 28-12) X (Moorpark X Blenheim 28-52)
1921Moorpark x P. I. 28954
1932(Moorpark 15-28 x P. I. 28954) x Bremner
1932Newcastle II 27-16 Japanese seedling
1923Royal X Blenheimψ
1933Royal X (Blenheim X Tilton 28-6)
1935Royal X Japanese seedling 26-18
1923St. Ambroise X Luizet
1931Sardinian X Japanese seedling
1925Sardinian X Royal
1925Sparks Mammoth X Blenheim
1935(Sparks Mammoth X Blenheim 37-59) X (Blenheim Moorpark 12-58)
1932(Sparks Mammoth X Blenheim 37-59) X Bremner
1923Tilton X Moorpark
1933(Tilton X Moorpark 30-23) X (Blenheim x Tilton 27-48)
1933Tunis 27-7A X (Moorpark X Blenheim 28-52)
1920P.I.34272T2 X Blenheim
1932(P. I. 34272 x Blenheim 12-50) X (Sparks Mammoth X Blenheim 37-60)

** Numbers following variety name refer to row and tree location of the parent.
*** “Japanese” variety from John Rock collection at Niles, Calif. Tree was not labeled, and nothing is known of its origin.
ψ['Blenheim' & 'Royal' (and possibly 'Patterson' for that matter) appear to be identical cultivars. -ASC]


Apricot Breeding Material at the New York (State) Agricultural Experiment Station, Geneva, N. Y.
Criscmelo seedling, P. I.34269, Geneva, Henderson, Ispharak Kandak (Russia), Murgab (P. I. 32834), Mulla-gadai (Russia), Paviot (Germany), Rittenhouse, Schik-Usbekistan (Russia), Toyahvale, Ungarishe.

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