Imágenes de páginas
PDF

28. Collateral Reading.—Corn Plants. Their Uses and Ways of Life. By F. L. Sargent. Boston: Houghton, Mifflin & Co., 1902. Twelfth Census of the United States. Vol. VI. Twelfth Census of the United States. Bui. 237.

Origin of Cultivated Plants. By Alphonse De Candolle. pp. 447-462. New York: D. Appleton & Co., 1902.

II.

IMPROVEMENT OF FIELD CROPS.

29. Changes in Farm Crops.—Probably there is no grain, grass, fiber or root crop cultivated in the United States which has not been greatly changed since it was a wild plant. In recent years many new varieties have been produced, differing in marked degrees from those formerly cultivated. Farmers generally do not actively interest themselves in the improvement of their crops; are not always careful to maintain them in their present standard of excellence. Much less attention has been given to the improvement of farm crops than to the improvement of farm animals.

30. The Importance of Plant Breeding.—The individual plant is the result of two forces: environment (climate, soil, fertilizer, culture, etc.) and heredity (parents, grandparents, etc.). The increased yield of a crop by modification of environment, although a necessary process to successful agriculture, can only be accomplished by an expense more or less considerable. Heredity, however, is a silent force, which acts without expense. If a plant be discovered that would produce because of the force of inheritance only one grain of maize more on each ear than at present, it would be capable of increasing the maize crop of the United States five million bushels of maize, not next year alone but for years to come. This is the significance of improved seed.

"The vast possibilities of plant breeding can hardly be estimated. It would not be difficult for one man to breed a new rye, wheat, barley, oats or rice which would produce one grain more to each head, or a corn which would produce an extra kernel to each ear, another potato in each plant, or an apple, plum, orange or nut to each tree. What would be the result? In five staples only in the United States alone the inexhaustible forces of Nature would produce annually without effort and without cost:

5,200,000 extra bushels of corn,

15,000,000 extra bushels of wheat,

20,000,000 extra bushels of oats,
1,500,000 extra bushels of barley,

21,000,000 extra bushels of potatoes. "But these vast possibilities are not alone for one year, or for our own time or race, but are beneficent legacies for every man, woman or child who shall ever inhabit the earth. And who can estimate the elevating and refining influences and moral value of flowers with all their graceful forms and bewitching shades and combinations for color and exquisitely varied perfumes f These silent influences are unconsciously felt even by those who do not appreciate them consciously, and thus with better and still better fruits, nuts, grains and flowers will the earth be transformed and man's thoughts turned from the base destructive forces into the nobler productive ones, which will lift him to higher planes of action towards that happy day when nun shall offer his brother man not bullets and bayonets, but richer grains, better fruits and fairer flowers.

"Cultivation and care may help plants to do better work temporarily, but by breeding, plants may be brought into existence which will do better work always, in all places and for all time. Plants are to be produced which will perform their appointed work better, quicker and with the utmost precision." 1

31. A Maize Breeding Farm.—A company in Illinois has a tract of 27,000 acres upon which they propose, if possible, so to breed the standard varieties of maize as to give the greatest feeding value per acre. They propose to breed maize with varying per cents of fat or protein as seems possible by the experiments of the Illinois Station.2 If a company had proposed to breed Holstein-Friesians whose milk should contain a high per cent of butter fat it would not be considered remarkable, yet the definite breeding of farm crops is so unusual as to create great interest in this new enterprise. The fundamental principles in breeding are the same whether applied to plants or animals. The study of tha principles of breeding especially as they apply to animals is a recognized part of courses in agriculture. No attempt will be mr.de in this chapter to discuss these principles but merely to point out some of the practical applications to plant breeding.

32. Application of Principle Delayed in Plants.—A number of circumstances have prevented the application of the prin

1 Luther Burbank

2 In referring to the Agricultural Experiment Stations under government and state control the word "Station" only will be used for the purpose of brevity.

ciples of breeding to plants, although they have been applied to the breeding of animals for many years. Among the circumstances are the following:

1. Lack of knowledge of the sexuality of plants until recent times.

2. Difficulty of control in breeding plants.

3. The selection is made from seeds which are embryos and not mature individuals.

The last two circumstances apply much more to some plants than to others. They apply with special force to ordinary field crops.

33. Sex.—The sexes in animals must have been known from the earliest times. Camerarius first published experimental proof of the sexuality of plants December 28, 1691. It was not until after this discovery that the function of pollen and its necessity to seed formation was understood. It will be readily appreciated that this knowledge did not become general among the growers of the staple crops until much more recent times and is perhaps still not understood by many. Thus there has been more or less systematic breeding of animals for 4000 years, while the mating of plants has not been practiced for more than two hundred years.

34. The Difficulty of Control in Breeding Plants.—The pollen of plants cannot ordinarily be confined, while the male domestic animal can be tied up by a halter or confined in a yard. In some plants like maize which is wind-fertilized we have no knowledge of the plant from which the pollen came and consequently no knowledge of the characteristics of the sire. In other plants like wheat that are self-fertilized two individuals cannot be mated without resorting to artificial means.

35. The Seed an Embryo.—The selection is usually made from the seeds. The seed is an embryo, not a mature individual. The characteristics of the mature chicken cannot be fully foretold by looking at the egg. The seed must be grown and the plant observed through youth, maturity and old age before the characteristics of the individual plant are fully known. The individual animals are constantly under the eye of the successful breeder. The poorer animals are rejected and only the better animals mated. In the case of plants there is not only usually no mating, but the mature individual from which the embryo is obtained for the subsequent progeny is unknown. This is not quite so true of maize as of the other cereals, because of the method of harvesting the crop. Even if the large ear of maize is a measure of the productiveness of the individual maize plant, the character of the sire is unknown. In the case of the other cereals, or of potatoes, the size of the grain or tuber is no necessary measure of the productiveness of the parent. A small grain from a fine, well-bred individual is better than a large grain from a poor, indifferently-bred individual. Other things equal, a small tuber from a large hill of potatoes is better than a large tuber from a small hill. In case the large and small seeds come from equally good heads of wheat, which will probably be the case under average conditions, the large seeds may perhaps give the best results, especially as under field conditions the larger size may be of advantage in enabling the plant to get a more vigorous start. Specific proof of this is, however, lacking. Hays believes it to be established that the best heads of wheat, as well as best plants, should be selected. In the case of maize the butt and tip grains have been found to be substantially equal to the middle grains of the ear. (272) To succeed in plant breeding the seed must be selected from individuals which possess the characteristics it is desired to perpetuate.

36. Examples of Improvement or Modification in Plants.—

Many of the modifications which have taken place in plants during cultivation by man may be said to be unconscious. At least there was no definite plan to accomplish the results attained.

« AnteriorContinuar »