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258. Breeding for Composition.-Hopkins found that when analyses were made of different samples coming from a considerable number of ears that the composition of the grain was quite uniform. When, however, samples were taken separately, even from different ears of the same variety, there were considerable differences in the composition. Some variation was found in the composition of grains from the butt, middle and tip third of the ear, but when one or more rows were taken throughout the whole length of the ear the composition of this sample was found quite accurately to represent the whole ear. He further established the fact that if the grains of ears varying in composition were grown separately, this difference in composition would be found in the resulting crop. It was thus established that composition was hereditary. He also showed that the composition would be determined in considerable measure by the physical distribution of the parts of the grain.

259. Breeding for Fat.-As thirty-five per cent of the embryo is fat and as eighty to eighty-five per cent of all the fat of the grain is in the embryo, it is evident that grain with large embryos would contain larger percentages of fat than those containing small embryos, unless the per cent of fat in the embryo itself varied largely.1

Beginning with the same variety of maize, ears were selected four years for high fat and low fat content. Then rows were planted with both kinds of maize, every hill having each kind of maize just far enough apart to identify the stalks. Thus they were grown in the same season, in the same soil and under the same cultivation. The resulting crop from maize selected for low fat content contained three and eight-tenths per cent of fat; that for high fat, five and eight-tenths per cent of fat. In other instances there have been brought about

1 The investigations of Hopkins appear to show that large embryos contain a larger percentage of fat than small embryos. Ill. Bul. 87, p. 105.

2 Ill. Bul. 87, p. 100.

variations in content of fat ranging from two and a half to seven per cent.

260. Breeding for Protein.-The relative proportion of glossy and white endosperm varies largely in the grains of different ears of the same variety of maize. In an average ear of Burr's white (dent variety) ten and two-tenths per cent of protein was found in the glossy endosperm and seven and eight-tenths per cent in the white endosperm. (226) Hopkins finds forty-two per cent of all the protein of the grain in the endosperm, and, also, holds that the aleurone layer, which also has a high per cent of protein, is larger in maize selected for high protein content. As the ratio of glossy to white endosperm is readily estimated by making selections of a few grains from each ear,

The grains on the left contain the higher percentage of protein indicated by the higher proportion of glossy or corneous endosperm as compared with the white or soft endosperm, and, also, possibly, by the larger embryo. (After Hopkins.)

assuming the above propositions established, maize may be bred for high or for low protein content. By this method, maize has been bred which contains but six and seven-tenths per cent of protein and as high as fourteen and four-tenths per cent.

Since the embryos contain a higher per cent of protein than the glossy endosperm and about the same percentage as the aleurone layer, it has been suggested that the variations in the per cent of protein were largely due to variations in the size of the embryos. Hopkins, however, has gone into a rather elaborate investigation to show that variations in the percentage of protein are due primarily to variations in the glossy endosperm and the aleurone layer and only secondarily to the variations in the embryo. 1

261. Breeding for Starch.-In order to breed for high starch content, we have only to breed for low protein and low oil content, as, practically speaking, the percentage of carbohydrates (principally

1 Ill. Bul, 87, pp. 96-101.

starch) is usually inversely proportional to that of the protein and fat. If maize were bred for the manufacture of starch or glucose, only low protein content would be desired, since the fat or maize oil, which is a by-product of the manufacture of starch, is worth more per pound than the starch.

262. Advantage of Breeding for Composition.-Throughout the North Central and Eastern States, and especially in those States which raise a great surplus of maize, stock foods generally contain too small a proportion of digestible protein. The protein is, therefore, the most expensive ingredient of stock foods, being several times more expensive per pound than maize itself. The raising of maize with a higher percentage of protein would reduce the need of purchasing more expensive nitrogenous foods, and would thus cheapen the food supply, provided the yield of maize is not reduced as the per cent of protein is increased. In the Southern States, the food supply for live stock is highly nitrogenous, due to large surplus of cotton seed, cottonseed meal and cowpeas. In this section, a high starch content may be desirable. Large quantities of maize are annually used for the manufacture of starch and glucose. The Glucose Sugar Refining Company1 says:

"A bushel of ordinary corn, weighing 56 pounds, contains about 4 1-2 pounds of germ, 36 pounds of dry starch, 7 pounds of gluten and 5 pounds of bran or hull, the balance in weight being made up of water, soluble matter, etc. The value of the germ lies in the fact that it contains over 40 per cent of corn oil, worth, say, 5 cents per pound, while the starch is worth 1 1-2 cents, the gluten 1 cent and the hull about 1-2 cent per pound.

"It can readily be seen that a variety of corn containing, say, one pound more oil per bushel would be in large demand."

263. Disadvantage of Breeding for Composition.-One disadvantage of breeding for composition and yield at the same time is that breeding for two characteristics at one time is several times more difficult than breeding for one. An objection to breeding for high protein is that the amount of nitrogen re1 Ill. Bul. 82 (1902), p. 526.

moved from the soil will be increased, unless the yield of maize is decreased. No results have been reported of the influence upon yield of breeding for high protein or other modifications in composition. Whether it is better to raise the surplus nitrogen needed in leguminous crops like clover, alfalfa, soy beans, cowpeas, field peas, etc., and to raise maize primarily as a source of easily digestible carbohydrates, will need to be settled by each grower in accordance with local conditions, assuming that composition has no influence upon yield.

264. Methods of Breeding.-Breeding for composition has served to call attention to the method of testing hereditary power, whether the character to be tested was high protein, fat or yield.

After several ears of maize have been selected for high protein, it becomes necessary to determine whether they will reproduce ears with high protein, and also to place the plants produced from such selected ears where they will be fertilized by pollen from plants having high protein content. If this is an advantage in the case of ears selected for high protein, it is also an advantage for ears selected for high yield. Large ears may be the result of environment or may be due to hereditary power. Of two ears of equal merit (as, for example, size), one grown on very rich soil and the other on ordinary soil, the latter should be preferred for seed.

265. The Breeding Plat.-Assuming total yield of grain to be the character bred for, the following is an outline of plan to be followed in the breeding plat, the details to be modified according to circumstances:

(1) First carefully consider the variety of maize best suited to conditions. Do not waste time improving a poor variety or strain. Having selected the variety, it will generally be wise to grow no other.

(2) Select 100 ears of perfect vitality of this variety. Weigh each ear separately and arrange in order of weight.

(3) From these 100 ears select forty nearest the ideal sought, giving due importance to weight of ear, but not neglect. ing other qualities.

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58

55

50

ROWS1--23

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(4) Next shell each ear separately, weigh cobs and determine total weight and per cent of shelled grain to ear. weight of grain is more important than the per cent. no necessary relation between per cent of grain to ear and yield. Large cobs may, however, be objectionable for other reasons, as, for example, their influence upon maturity and preservation of the ear. the information obtained, select twenty-five out of the forty ears

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and number ears 1 to 25,
ing the best ear No. 13, the
next best ears 12 and 14 and

the poorest ears 1 and 25.

POUNDS PER ROV

EARI 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
ROWS 26-50

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(5) Lay off a piece of uni- Diagram showing the influence of heredity and

environment upon yield of maize. Curves show yield per row in pounds of field cured grain of fifty rows grown from twenty-five different ears of the same variety. Rows No. 1 and No. 26 grown from seed of ear No. 1; rows No. 2 and No. 27 from ear No. 2, etc. The rows were each fifty hills long, and each hill, with very few exceptions, had exactly three stalks per hill. Grown in Fayette county, Ohio, by L. H. Goddard.

form land fifty hills square and plant rows 1 and 26 to ear 1; rows 2 and 27 to ear 2, until ear 25 is planted on rows 25 and 50. Place five grains in each hill, and when plants are three to four inches high, thin so that each row has 150 plants. If this plat of maize is planted by itself, four rows should be planted clear around the plat from what is left of the twenty-five selected ears. In many cases the most practical way will be to plant the plat in the body of a field containing the ordinary crop, which will be the same variety. The breeding plat should not be within twenty rods of neighbor. ing maize fields, especially if the variety is different.

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