Horticultural Society of New York
Int'l Conf. on Plant Breeding and Hybridization (1902)
CORRELATION BETWEEN DIFFERENT PARTS OF THE PLANT IN FORM, COLOR, SIZE AND OTHER CHARACTERISTICS.
S. A. Beach, Horticulturist,
New York State Experiment Station, Geneva, N.Y.
Work in plant breeding, when considered from the standpoint of the worker, falls into two general classes. In one class the effort is to originate an improved strain or variety; in the other the object is to learn the philosophy of plant breeding, to discover the scientific principles involved and to illustrate the application of these principles. Immediate practical results are sought in one case; in the other a knowledge of the laws of plant breeding, by means of which continued progress may be made. The former, if successful, gives only something transient. The improved variety or strain which is produced will doubtless be superseded in time by something better, as the evolution of cultivated plants progresses. Such is the verdict of horticultural history. We look to the other kind of effort for the more permanent and eventually more rapid progress in breeding plants. It is the purpose of this essay to call attention to a question, the investigation of which may yield results of general importance and permanent value, namely, the extent to which correlation between different parts of the plant in form, color, size and other characteristics may be regarded as a significant factor in plant breeding. Nurserymen, seedsmen, fruit growers and gardeners know many instances of such correlation, and often take practical advantage of it when making selections for propagation, albeit perhaps unconsciously, and without formulating in words a definite expression of their judgment on this point. Scientific investigators have also occasionally recognized instances where correlation is of significance as a means of selection in breeding or propagating plants, but it appears that this subject has not been investigated as systematically and thoroughly as it should be.
In plant breeding the chances for originating an improved variety are in some degree proportionate to the number of seedlings produced. Other things being equal, the more numerous the seedlings subject to selection, the greater the probabilities of finding the improvement sought. But the more seedlings one undertakes to grow the greater the necessity of getting rid of the undesirable ones at as young a stage of growth as possible, and thus avoid the labor and expense of growing a great number of useless plants; therefore, a skillful breeder does not defer the process of selection till the seedlings appear, but exercises rigid choice, perhaps with the seed which is to be planted, and surely with the parents, or stock plants, from which he expects to take the seed, cions, buds or cuttings for propagation. Correlation of parts or characteristics in plants may be of use not only in selecting seedlings, but also in choosing the parents, and even in choosing the seeds which are to be used in breeding. Notice a few illustrations.
|1Geschwind, L., Rev. Gen. Chim. AppI., 3 (1900). No. 12. Cited in Exp. Sta. Rec. XIII: 526.|
Geschwind1 finds correlation between the structure and the sugar content of the beet-root. He states that, as a rule, high sugar content is associated with a small amount of woody tissue, and recommends that beets be selected for breeding which have but small amount of woody tissue, as shown by cross-section of the top.
LX (1901); 228.
CybeRose note: This fact was discovered by
Anderson-Henry (1861), who worked with McNab at the Edinburgh garden.
Henslow2 states that McNab finds that in breeding rhododendrons the best dwarf varieties are obtained by using pollen taken from the smaller stamens.
|3Swingle, W. T., Discussion on Plant Breeding at the New Haven meeting of A.A.A.C.E.S., Nov., 1900.|
Swingle3 states that in Europe certain plant breeders who had long been engaged in breeding grain for the increase of the percentage of protein found recently that a high nitrogen content of the grain is correlated with blue stemmed plants, and since making this discovery have been enabled to make more progress in three years in increasing the nitrogen content of the grain by plant breeding than they had in many previous years' effort toward the same object.
G., Jour. Roy.
Hort. Soc. XXIV: 85.
Henslow4 says that very dark crimson zonal geraniums are so nearly self sterile as to make seed raising difficult, the sterility being in proportion to the depth of color, which is correlated with proterandry. Paler varieties are more nearly homogamous and are very self-fertile.
Dr. G. L., in personal
communication to the writer, 1902.
Tinker5 states that male vines of Vitis bicolor, Mx. at all ages, have leaves more lobed or divided than pistillate vines of the same species, and that this distinction is discernible in seedlings when they have put forth the sixth leaf. In his work in breeding grapes he finds it practicable to discard male bicolor seedlings when the sixth leaf is formed.
C., cited in Exp. Sta. Rec. XIII (1901): 241.
7De Vries, Hugo, Die Mutationstheorie. Erster Band (1901): 77.
Debroyker6 has shown that correlation in length exists between the culm and the head and the upper internode and the head of the rye plant. He did not find, however, that heredity had any apparent influence on these features. Many instances exist of correlation between different parts of a plant in size, but not enough observations have been made to permit of general statements as to the full significance of this character in any particular class of plants. De Vries7 finds that there is a relation between the vigor of the plant in Oenothera Lamarckiana and the size, i.e., length and thickness, of the fruit. The larger and more vigorous the plant, the longer and thicker the fruit; the shorter the fruit, the weaker and more slender the plant.
In the vineyard of E. C. Gillett, Penn Yan, N. Y., is a vine of the Concord grape, from one side of which has appeared a sport, bearing much larger fruit and much larger seed than is grown on the normal portion of the same vine. Seedlings which I have grown from seeds produced by the sport are larger and more vigorous in type than those produced from seed produced by the normal canes. None of these seedlings has yet fruited. The fruit of Hercules grape, a labrusca-vinifera hybrid, has very large fruit and correspondingly large leaves. The same is true of Columbian Imperial, Pierce and other varieties which might be named. Delaware has small fruit and correspondingly small leaves; so also have Golden Gem, Golden Drop, Rebecca and others. In breeding grapes I have found among some very excellent varieties others that were exceedingly dwarfed in leaf and habit of growth. When such dwarf vines have been allowed to mature and bear fruit they have produced either small fruit, or small clusters, or both. Many hundreds of grape seedlings of known parentage which have been produced during the progress of my work in breeding grapes show that size and color of foliage, vine and fruit tend to be transmitted to the offspring with considerable uniformity—so much so, that the entire lot of seedlings of any particular parentage, whether pure bred or cross bred, when viewed as a whole, is usually of a characteristic type and distinct from the seedlings of other, albeit nearly related parentage. Similar results have followed the work with gooseberries.
It should be remarked that in making observations on correlation of parts as to size it is important to give due consideration to the species or group features, if the individuals compared represent different groups. For example, some varieties of Vitis aestivalis Mx. may have larger foliage, but smaller fruit, than certain varieties of Vitis labrusca, yet within the limits of the species the larger types of leaf may be found associated with the larger types of fruit, and the smaller types of foliage with the smaller types of fruit.
With the peach it is easy to find many illustrations of a correspondence in size between the foliage and the fruit. Compare, for example, the type of foliage found on Elberta, Crawford and other large fruited varieties, with the smaller, narrower leaves found on smaller peaches, like Golden Prolific and Hill's Chili, and especially on the seedlings commonly called "natural fruit," which bear exceedingly small fruits.
Finally, on the question of the correspondence in size of different parts of the plant the evidence at hand, although not sufficient to support a general statement that it dos exist, gives enough indications that it may be found to make the subject worthy of investigation.
The question of correspondence in color between different parts of the plant will now be taken up. In 1894, and again in 1897, a large number of varieties of apples in one of the orchards of the Geneva (N. Y.) Experiment Station were examined with reference to the color of the blossoms and blossom buds. Space permits but a summary of results. Two hundred and ten varieties were under observation. There appeared to be no constant relation between the color of the bloom and the color of the fruit, except that a large majority of the very pale or very nearly white blossoms were either on crab apples or Russian apples. One crab apple, however, was recorded as having pure white blossoms, while its fruit is well described by the name of the variety, which is "Blood Red."
Raspberries, Rubus strigosus and R. Idaeus and R. occidentalis, which bear so-called white or yellow fruit, have correspondingly paler foliage and paler canes than the black or red fruited varieties. So, also, the purple raspberries (R. occidentalis-strigosus or occidentalis-Idaeus hybrids) have a distinct tinge on the foliage and canes corresponding to the purple color of the fruit. I have never known any exception to the above statements.
Some roses with white blossoms have noticeably paler foliage than that of dark red varieties. Similar correspondence in color of blossoms and foliage has been observed among pelargoniums, cannas, asters and other flowers. Apparent exceptions are seen among some of the cross-bred perennial phloxes.
Grapes with pale foliage, so far as I have observed, have so-called white fruit, or, at least, do not have dark colored fruit; but the converse is not always true, for some Concord seedlings which have the white fruit have foliage nearly or quite as dark as the parent. In observing this feature the fully matured leaves should be examined. Many instances are known of white fleshed peaches having correspondingly paler leaves and bark than have the yellow fleshed peaches. There is also often a noticeable difference between the foliage of varieties having pale yellow or lemon yellow flesh or skin and those having darker yellow flesh.
|1Emerson, R. A. Horticulturist,
University of Nebraska.
Emerson1 writes me that there is a noticeable correlation between the color of flowers and the seeds of beans. Races, such as Jones, Davis, Navy, etc., which have white seeds, always have white flowers. Races that have black seeds, if memory serves me correctly, always have flowers that are strongly colored, e.g., Challenger Black. Races that have spotted seeds or seeds tinted usually have flowers also tinted. One cannot always tell, however, by the tint of the flowers the exact degree of tinting of shading of the seeds. In the Blue Pod there is a correlation between the color of the flowers and foliage, as there is also with Scarlet Runner and White Dutch Runner. Seedlings of the last two are easily distinguished in one ease by the reddish color of the stems, in the other by their light green color. Races with spotted pods, like Horticultural, usually have spotted seeds.
|2Fraser, S. In personal communication to the writer.|
Fraser2 states that when the young stems or sprouts of the potato are either green or white, it is an indication that the blossom will be white. If the stems are colored the blossoms will likewise be colored. The statement is based on observations of about 280 varieties.
|3Dorner, H. B., Asst. Botanist,
Mr. C. W. Ward, Queens, N, Y., has called my attention to a correlation of color between the root and flower of the carnation, the white, yellow or red flower being associated with corresponding differences in the color of the root. Dorner writes me that he3 has noticed that carnation plants bearing white flowers have white roots; those with yellow flowers have yellowish roots; those having the various shades of pink and red have pinkish roots, and those with crimson and purple flowers have dark roots of a dull purplish red. Plants having variegated red and white flowers show roots varying between pink and white. Crimson and purple varieties often show a purplish tinge at the nodes.
The above observations are made only for varieties having solid colors, and exceptions may be found, but none have yet been noted.
In tulips the color of the flower may find a correspondence in the color of the bulb.
Grepr. Reprint in Jour. Roy.
Hort. Soc. XXVI. (1901) :6.
Lastly, let me quote from Mendel's observations on Pisum, as stated in his list of characters selected for his famous Experiments in Plant Hybridization.1 Among other characteristic differences in the varieties chosen for the experiments he mentions those which relate:
"To the difference in the colour of the seed-coat. This is either white, with which character white flowers are constantly correlated; or it is grey, grey-brown, leather-brown, with or without violet spotting, in which case the colour of the standards is violet, that of the wings purple, and the stem in the axils of the leaves is of a reddish tint. The grey seed-coats become dark brown in boiling water.
"To the difference in the colour of the unripe pods. They are either light to dark green, or vividly yellow, in which colouring the stalks, leaf-veins and blossoms participate."
Finally, on the question of correspondence in color of different parts of the plant, as was the case concerning size, it may be said that the evidence at hand, although not sufficient to support a general statement that such correlation always exists, certainly gives strong enough indications that it may be found to make the subject worthy of investigation.
L. H. Bailey: Does the speaker find any correlation between the size of the leaves and the quality of the fruit? which after all is what we are after.
S. A. Beach: Not necessarily. I believe that we may find a correlation between the texture, and the texture of the fruit.
W. Bateson: In connection with this list of correlations which Mr. Beach has cited, there is a curious paradoxical case in the pea, Pisum sativum; the purple axil is correlated with a purple flower, while a white axil is correlated with a white flower. Curiously enough, in the sweet pea that is not necessarily the case. There are deep purple varieties of sweet pea which do not necessarily have a purple axil at all; but the contrary is not the ease; there is no very white sweet pea which has a purple axil. I mention that as a paradoxical case which does not follow the same rule.
N. E. Hansen: In the fall of 1898 I called on Mr. Gideon at his home in Excelsior, Minnesota. For the benefit of Eastern people I will say that he has raised more apple seedlings than any one else in the West. He said that it he had a seedling in which the leaves were small he threw it away always, while any seedling with large leaves he kept; he had found that the tendency was toward larger fruit.
H. H. Groff: I would like to reconcile the reasoning of Professor Beach that the experimental worker is likely to overtake his more strenuous brother for the reason that the latter's efforts will soon be overtaken by his later and greater activity, I understand that that is the reasoning which he advocated, thereby sweeping away the experience of Mr. Burbank, Mr. Hays, and, I would like to add, myself.
S. A. Beach: I had no idea of undervaluing the work of the practical plant breeders; I believe in it thoroughly, and my only point was that I wished their assistance in trying to secure all the information possible, so that we can get at all data possible, classify it and put the whole business of plant breeding upon as nearly scientific a basis as possible. When we have done that, I think we can make more rapid progress than without it.