Problems of Method pp. 20-25
Much better and more reliable results are obtained from breeding new varieties with a special inclination toward earlier bearing. This is achieved by the expedient selection for crossing of parental pairs already possessing the qualities we require. The fact is that in examining the diverse qualities of all varieties of fruit plants in general, and of apple and pear trees in particular, I paid attention to those which are most suitable for solving the problem facing us. I shall explain in greater detail. All our apple-tree varieties and, in part, our pear trees, have to be divided into four groups: the first group covers varieties whose trees form fruit buds when the wood of the sprouts is three years old; the second group covers trees which form fruit buds when the wood is two years old; the third group covers those which form buds on the previous year's one-year-old shoots, and the fourth group covers varieties, extremely rare, it is true, whose trees produce fruit buds on young sprouts that have grown in the spring of the same year.
Fig. 1. Development of a fruit bud of Shafran-Kitaika:
|A—Growth shoot with two-year-old wood; B—fruit bud formed on one-year-old wood; C—fruit set on one-year-old wood; D—growth shoot in spring of same year formed from fruit bud alongside fruit; E—blossoming of upper part of this young shoot|
Well then, the trees of the varieties of the fourth group are distinguished for their regular, annual and abundant yield. Two-year-old bud grafts of these varieties already bear fruit. Pippin Shafranny, the new variety which in the first bearing year bore fruit on a young sprout of that year’s growth belongs, in part, to this category. In the following years fruit buds were also formed on the wood of the previous year. This variety is notable to this day for its abundant yield year in and year out. An analogous property is also met with in the Shafran-Kitaika (see Fig. 1), a new variety bred by me. From this variety's fruit bud, marked with the letter B, after the blossoming and the formation of the fruits C, there appears next to the fruits a new sprout D on which blossoms E develop anew, and fruits are formed for a second time.
We find this property to a still more considerable degree in the Golden Delicious apple tree, a chance growth from a seed in West Virginia.
By selecting such and similar varieties to serve as paternal and maternal parents and crossing one with the other we can select from the hybrid seedlings specimens with the most strongly developed property of early bearing in varieties that can yield fruit on two-year-old grafts.
This is the only method by which we will fulfil that very worthy task: "To breed early- and abundantly-bearing varieties."
To fulfil this task seeds of the original fruits of Golden Delicious apples brought from America by Academician N. I. Vavilov were planted in the spring of 1933. A hundred seedlings were obtained possessing identical habit both as to form of leaves and their petioles and as to form of sprouts and the buds on them, which proves that here selfing, i .e., self-fertilization, took place. Further observations will show whether this assumption is correct or not. This is particularly important to us, if for no other reason than that otherwise we shall be unable to obtain this original American variety, inasmuch as the dozen trees of this variety received from America have leaves of different forms, and hence raise a doubt as to the genuineness of the variety. Besides, their resistance to the climatic conditions of our locality will be much lower than that of our own seed-bred variety.
Fig. 2. One-year-old seedling of Golden Delicious apple in loose, rich soil
Fig. 3. One-year-old seedling of Golden Delicious apple in poor, dry soil
In addition, as may be seen from the illustrations (Figs. 2 and 3), a hitherto unknown phenomenon can be observed in the Golden Delicious seedlings. It is expressed in an especially vigorous development of the root system, as a matter of fact so vigorous that the roots develop even above the surface of the ground along the lower part of the stem not only above the spot where the cotyledons are found but also between the lower true leaves of the seedling. This already indicates the specific structure of this type of apple tree, a fact extremely important for hybridization in the future, for crossing it with other varieties, for breeding by selection particularly prolific and precocious varieties.