Recent Basic Information on Breeding Peaches

Several varieties were introduced during the war period. Thousands of seedlings resulting from crosses made before the war have been gone over and the most promising ones selected for further trial. The actual crossing of varieties and the detailed work connected with that process have not been conducted on so extensive a scale as was done just before the war. Lack of workers and demand for work of more immediate war value reduced the breeding program in the Department as well as in most State experiment stations. Through the study of progeny of crosses made previously much has been learned that should aid in selecting parents to obtain the desired characters in future seedlings.

The development of superior varieties in the future should be more sure and rapid as a result of our knowledge of inheritance of characteristics of parents. Several years ago investigators at the New Jersey Agricultural Experiment Station found that pollen fertility was a dominant character in peaches and evidently controlled by a single pair of genes. Now, because of the large number of individual progeny records made, we can classify- a great many varieties on the basis of how they transmit pollen sterility to their progeny. We also know that varieties vary considerably in the transmission of the chilling required to break their rest period. For example, Halehaven gives a wide variation in chilling requirements among its offspring. This is an important character in Southern peach areas, and until recently it was largely a matter of chance whether an improved variety could be grown successfully in the southern parts of Georgia, Texas, and California, or anywhere in Florida.

Genetic studies have recently been made on the inheritance of such characters as bud set, time of ripening, size and shape of fruits, firmness, color of flesh and skin, amount of fuzz on the skin, and freedom at the stone. We can select parents with more and more confidence in obtaining the desired combination of characters.

We now know that when certain parents are used in crosses there will be a wide variation in some characters among the offspring; when others are used the variation is much less. Thus we can estimate the number of progeny desired to obtain the character or combination of characters desired. In some crosses several thousand offspring seem none too many, whereas in others only 25 may be enough.

A modern method of peach breeding can be illustrated by the development of the Dixigem by the Department. The first peaches to reach Northeastern markets in fairly large quantities have long been those from southern and south-central Georgia. Some of the more popular varieties have been Mayflower, Uneeda, Early Rose, and Early Wheeler (Red Bird). Because of their earliness, these white varieties have been in demand by consumers and have been profitable to the peach grower during certain years. Those who eat peaches prefer the larger, yellow-fleshed varieties and higher quality. Those who grow them want more dependable bearing, higher yielding, firmer fleshed varieties, and of course they want varieties that as nearly as practicable fulfill the consumer's ideal. When the peach-breeding work at Beltsville was started in 1936 by F. P. Cullinan, one of his major objectives was to breed better peaches for the South. One of the major problems faced that first year was which parents to use in their crosses. Much less was known then than now about the merits of different varieties as parents. About 75 crosses were made in 1936 and several varieties were self-pollinated. Among the many parents used were Halehaven, South Haven, and an unnamed seedling selection of a cross between Admiral Dewey and St. John. This last selection was a result of some of the earliest peach breeding by the Department, a cross made by W. F. Wight in 1920 at South Haven, Mich.

Peach breeding was started in 1936 at Fort Valley, Ga., the center of the major peach regions that specialize in the production of early peaches. When J. H. Weinberger began the work there, he took with him the peach seeds resulting from the crosses made at Beltsville the previous spring. The seeds were germinated and grown in pots in the greenhouse during the late winter, and early spring of 1937. In April 1937, when the danger of frost was over, the trees, then about 18 inches high, were transferred to the field. There they were planted 3 feet apart in rows 12 feet apart. Next came the years of selection of the best progeny. In the meantime other crosses were made at Beltsville, Fort Valley, and in California.

Among the progeny of the 1936 crosses were several that seemed superior to the early-ripening commercial varieties of the same season grown in central Georgia. They could not all be named, but the best one for a particular season and purpose had to be selected through trial year after year. A few trees of each of the more promising progeny were tested on the grounds of the United States Horticultural Laboratory at Fort Valley, some were sent to State experiment stations, and some to the Plant Industry Station at Beltsville. Large tests were made in cooperation with fruit growers in Georgia.

As the testing progressed, some of the selections were discarded each year because of one or more faults. Finally, in 1944, the one tested under the number FV 8-35, resulting from a cross of the unnamed seedling of Admiral Dewey X St. John with the South Haven variety, seemed best for its season. It was named Dixigem, and whatever budwood was available was furnished those who wanted to propagate it. The popularity of Dixigem is indicated by the 50,000 trees budded in 1944 and 100,000 in 1945. Dixigem is far from being the perfect peach, but it seems superior to other early varieties in the South, where it has been tested most.