Tilton's Journal of Horticulture and Florist's Companion, 7: 164-166 (1870)
Experiments In Hybridizing The Grape
Dr. A. P. Wylie, Of South Carolina.
We present the following extracts from Dr. Wylie's letter, in the Proceedings of the American Pomological Society, and regret that we have not space for the whole. The discoveries he has made as to the difficulty of hybridizing the Scuppernong grape, and the causes of it, are very interesting as well as curious.
"I find that all the natives with which I have experimented hybridize freely with the foreign (Vitis vinifera), except the Scuppernong (Bullace). I have impregnated successfully with foreign pollen the following, viz.: Vitis aestivalis, several varieties; Vitis Labrusca, many varieties; Vitis cordifolia, four varieties; also successively fertilized Vitis vinifera with each of the above species; also many hybrids with each other and with pure species, and many natives with each other; also numerous hybrids with hybrids, and fixed species. The Scuppernong appears to be a very distinct species, and least capable of all others of hybridizing with other species.
"My experience goes far to establish the following facts, viz.: First, that we cannot fertilize the Scuppernong with pollen from any other species or their hybrid varieties, as I have repeatedly failed to do so under the most favorable circumstances; also failed, after numerous trials, to fertilize Scuppernong with male (staminate) hybrid Scuppernong. Second, that we can impregnate the foreign (Vitis vinifera) with pollen from the Scuppernong; as I have had the plants growing ever since 1861, but none have borne fruit. Third, that we cannot impregnate either Labrusca, AEstivalis, or Cordifolia, as I have repeatedly failed in the attempt. Fourth, that you can fertilize both native and foreign, and their hybrids, with male (staminate) hybrid Scuppernong pollen, as I have often done. Fifth, that no first crop of Scuppernong and foreign will produce a prolific fruit-bearing plant, as those have invariably either proved to be male (staminate) or hermaphrodites, with male and female organs of reproduction (stigma and stamina) defective, consequently bearing no fruit. It is true I have seen one of these hermaphrodites bear a few berries, by applying pollen from a grape vine of a different variety. (See Gardener's Monthly, 1868, p. 153). Sixth, that you can produce a prolific hybrid Scuppernong by impregnating the foreign (Vitis vinifera) with pollen from hybrid male (staminate) Scuppernong, as I have had a hybrid thus produced bear perfect fruit, with perfect seed, for the first time, this last summer. I have also plants of Herbemont, Delaware, Lenoir, Clinton, and others, impregnated with the same pollen, which have every appearance of bearing plants, but were not old enough to bear this summer.
"There appears to be a mechanical difficulty, which limits the production of hybrids with the Scuppernong and other species. Suspecting some difficulty of this kind from my repeated failures, I requested my friend Dr. T. T. Robertson, of Winsboro, S. C, a gentleman of high respectability and intelligence, who was familiar with the use of a microscope of high power, to examine for me the various kinds of grape pollen. He writes thus: 'I have examined every variety within my reach, — native, foreign, wild, tame, winter, summer, and all, — and had come to the conclusion that grape pollen was grape pollen, and nothing more, the world over, and that there was no difference whatever in the size, shape, color, etc., of the pollen grains; but when I came to the Scuppernong (the very one you seem most solicitous about), I did find a difference. In this the pollen grains are smaller and more spherical than any of the others. The rest (which all look alike) are more oblong, with a greater longitudinal diameter than the Scuppernong. The transverse diameter, I think, is about the same in all. If there is any difference, the Scuppernong is a shade less; and this may account for the result of your experiments; that is, the ability to impregnate other species with the pollen of the Scuppernong, and the inability to do the reverse.
" 'I believe the theory is, that the pollen grains must pass through the style of the pistil, and come in contact with the ovule at its base, to effect its fecundation. Now, if the pollen grains are smaller in the Scuppernong, the inference is, that the canal through which they have to pass is also smaller than that of the other varieties; and thus may be explained the result of your experiments. The smaller grains may pass through the larger tubes; but the larger grains cannot pass through the smaller tubes.'
"Some time after this I sent him some hybrid Scuppernong pollen to examine. He writes thus: 'Dear Sir, I have examined the pollen, and think I could have diagnosed it as a hybrid or mixed specimen. The difference between the Scuppernong and all other varieties that I have examined is very distinct, and so much so that I believe I could detect a single grain of it in any specimen that might come in the field of view.
" 'The specimen sent contains a very large proportion of grains resembling the Scuppernong, and a much smaller proportion resembling those of all other varieties that I have examined. I send you a rude sketch of the appearance, in outline, of the various kinds; that is, the Scuppernong, all other varieties, and the hybrid Scuppernong. You will perceive that the Scuppernong grains are more spherical, and less uniform in shape, than the others. The long diameter is considerably less; the short diameter about the same, or probably a shade less. I have no micrometer, and therefore cannot give you the dimensions; can only judge from the eye. The pollen grains appear, in outline, to be oblong, elliptical, or oval. If I were anything of a botanist I could probably write more intelligibly upon this subject.'
"Still, notwithstanding my failures and the revelations of the microscope, I have broken the barrier which separates the Scuppernong from the other species of grapes, and produced one prolific plant, with well-formed berries — fine, high musk flavored fruit, and perfect seed; the bunch containing from twenty to twenty-five berries, and ripening in succession as the Scuppernong; and who can predict the fine varieties that may be acquired in future by producing hybrids of this species and planting their seed? for I find that there is no end to the sporting of varieties raised from seed of hybrid plants, or the crosses between two hybrids.
"The Scuppernong is one of the most distinct and remarkable species in the world; and in loamy, porous soil, or even in the damp, sandy soil of the South, where other kinds cannot flourish, it flourishes and bears incredible quantities. It never rots, and has no disease that I ever heard of. The aegeria, or grub, so destructive to the foreign and other soft-wooded species, never touches it. I have seen it bear and flourish with its roots entwined among the roots of other species, completely honeycombed with the grub."
See also, Wylie: Hybrid Grapes (1868)
Ravenel: Some of Dr. Wylie's Hybrid Grapes (1870)
Elliott: Experiments in Hybridizing the Grape (1870)