Zoe 2: 108-111 (1891)

THE RECIPROCAL INFLUENCE OF STOCK AND SCION
GUSTAV EISEN

The following instances of the influence of stock upon scion, or vice versa, have come under my personal observation. They clearly show that there exists a strong reciprocal influence between scion and stock, which, when more fully understood, may be of practical value in the artificial production of new horticultural varieties.

Some ten years ago I had in my garden a Mandarin orange tree, budded on sweet California stock. This stock is simply produced by sowing the seed of any of the commercial oranges, and the seedlings are afterwards budded with improved kinds. If any of these seedling are allowed to fruit as seedlings, the fruit will be found to more or less resemble the parent orange; that is, it will be of fair or large size, with sweet meat and thick skin — the seedling orange of our markets.

The Mandarin orange in question was a little tree, nine feet high and quite bushy, and had borne a good crop of oranges for at least five years. Its oranges were characteristic of the Mandarin variety — small, round, compressed, and with the skin peeling off like a glove — hence the name "Kidglove orange," under which this and similar varieties are known.

One winter we had a heavy frost and the Mandarin was greatly injured. When the time for making new growth came I found the top almost dead, and only one feeble shoot coming out above the bud. The remainder of the top died, and was cut off in order to save the new shoot. This grew rapidly, and at the end of the season had attained the full height of the old tree, with several large side branches. But the leaves of the new standard did not resemble the leaves of the old Mandarin tree, but were quite similar to those of a common sweet seedling orange. So much did they resemble the sweet stock that I thought, and continued to think for some time, that all of the Mandarin part of the tree had been killed, and that the new tree was produced from below the bud.

Next year the tree produced fruit in size and quality intermediate between a sweet seedling and a Mandarin—much more resembling a sweet seedling, only distinguished by its smaller size; which, however, was several times larger than a large Mandarin orange. The meat and skin showed every characteristic of the common sweet orange. The year following the leaves became smaller, and the oranges almost identical with the original Mandarins. The third year the fruit and other parts of the tree had regained all their Mandarin characteristics. Ever since, this tree has produced Mandarin oranges of the same size and quality as before it was injured by frost.

My theory of the change from one variety to the other is simply this: The frost killed the largest part of the Mandarin tree, only one bud surviving. The shoot produced by this bud was so influenced and overpowered by the strong sweet seedling root that it lost part of its own characteristics, which were only regained gradually as the Mandarin shoot became more vigorous and could exert its old influence over the root.

About twelve years ago my attention was called to a very large grapevine of the variety known as Flaming Tokay, which had been grafted on the wild grapevine of California — Vitis Californica. The vine must have been some ten years old, and covered part of a veranda with luxuriant foliage, and large annual crops of its characteristic and magnificent flame-colored bunches. From the root of this vine, and as it was afterwards ascertained, several inches below the graft, a shoot had sprung up which partook of the peculiar characteristics of both the graft and the root. The new shoot was, as regards leaves, intermediate between the Flaming Tokay and the Californica. The next year this shoot-branch produced fruit which also showed characteristics of both varieties, but which much more resembled the Californica than the Tokay, and accordingly proved of no particular value. Some cuttings of the new sport were propagated and produced a similar hybrid grape, but as far as I know no attempt was made to seed the new grape. According to my theory the old Flaming Tokay grape exerted a large influence on the Vitis Californica root on which it was grafted, and the sport produced was a sap-hybrid between the graft and the stock.

In 1886 I had occasion to assist a friend in grafting a number, one hundred or more, of Sultana grape vines which he desired to change to Muscatel Gordo Blanco, like the remainder of the vineyard. The Sultana vine has large pale green leaves, long slender shoots, and large compact bunches of very small berries. The Muscat is the opposite of this: leaves medium, deep green, short branches, and bunches compact and berries large. The Sultanas were cut down several inches below the ground and the Muscatel graft inserted, leaving no branch of the Sultana. The work was all very carefully done, and the grafts all "took." Two months later I went over the vines, only to find to my astonishment that all the tops of the vines were Sultanas, or apparently so. Upon examination, however, I found that all the grafts had taken, and that there were few if any shoots from the roots. My idea was then that the grafts had been mixed up, and that we had inserted Sultana grafts in Sultana stocks. However, as the vines grew I found a few months later several bunches of berries which in shape and size exactly resembled the Sultana, but which had a distinct and strong Muscatel flavor. Everything else about the vine, such as color and shape of leaves, size of branch, distance between the leaves, etc., was entirely characteristic of the Sultana. The following year the grafts began to regain their Muscatel characteristics, and the third year they had done so entirely, producing a good crop of Muscatel grapes.

I had in the meantime inquired among the other grape-growers, and inspected a large number of lately grafted vines. The variety that had been mostly grafted were Zinfandel vines, and the grafts were uniformly those of Muscatel. I found that several parties had made observations similar to my own, and saw here and there young vines which partook of the characteristics of the stock and the graft. Muscatels grafted on Zinfandel resembled that variety as to leaves, branches, and shape and size of berry and bunch, but never as regards color of berry and aroma. The color was always green, and the aroma Muscatel-like. In one or two seasons later these grafts had all lost their Zinfandel characteristics and produced regular crops of Muscatel grapes.

An explanation I believe is hardly necessary. The sap from the Zinfandel and Sultana roots respectively had during the first season so influenced the graft that it had partaken of most of the characteristics of the stocks. Only as the scions grew did they gain in strength, throw off the influence of the stock, and regain their characteristics as Muscatel grapes.

It is needless to say that the reciprocal influence between stock and scion may be taken advantage of in producing new varieties with valuable qualities. The hybrid grafts may either be propagated by themselves, if sufficiently valuable, or the fruit produced on them may be seeded and the new seedling watched for valuable characteristics. The frequency and facility with which grape scions partake of the characteristics of the stock is especially interesting, and should greatly facilitate the production of new varieties of greater economic value. 1 will here only point out the desirability of getting a hybrid between the ''Muscatel'' and the ''Malaga'' grapes, and the possibility of producing it by sap hybridization.