Hayes and Garber - Cucurbit Breeding
Hayes and Garber - Cucurbit Breeding Hayes and Garber - Cucurbit Breeding
200 BREEDING CROP PLANTS system of broad breeding, the use of a high-yielding, adapted variety, and the storage of the seed so that it will germinate vigorously are important practices which should be a part of each corn-breeder's plan. Relation between Heterozygosis and Vigor. In an earlier chapter the effects of self-fertilization in corn were discussed FIG. 45. Minn. No. 13 self-fertilized high protein strain No. 1. This strain has dark green leaves, medium sized ears and the tassels are somewhat scantily provided with pollen. and the hypothesis outlined that vigor in /*\ crosses was due to the partial dominance of linked growth factors. This question is of considerable importance from the standpoint of the corn breeder. The subject will be discussed under the following headings:
MAIZE BREEDING 201 1. Immediate effect of crossing on size of seed. 2. F! varietal crosses. 3. Isolation of homozygous strains. Immediate Effect of Crossing on Size of Seed. The question of immediate effect of crossing on size of seed has received considerable attention, and Carrier (1919) has recently considered this a main cause for the conflicting results of corn experiments. He demonstrated the fact that mixtures of seed of different strains gave higher yields than seed of a single strain and explained the results on the basis of increased yield due to the increased weight of the endosperm of varietal crosses as compared with normally pollinated seeds within a variety. Other investigations have partially supported Carrier's contentions. Studies of the effect of pollen of a different strain or variety on endosperm development are given in Table XLVIII. TABLE XLVIII. IMMEDIATE EFFECT OF POLLINATION ON ENDOSPERM WEIGHT Number of tests
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MAIZE BREEDING 201<br />
1. Immediate effect of crossing on size of seed.<br />
2. F! varietal crosses.<br />
3. Isolation of homozygous strains.<br />
Immediate Effect of Crossing on Size of Seed. The question<br />
of immediate effect of crossing on size of seed has received considerable<br />
attention, <strong>and</strong> Carrier (1919) has recently considered<br />
this a main cause for the conflicting results of corn experiments.<br />
He demonstrated the fact that mixtures of seed of different strains<br />
gave higher yields than seed of a single strain <strong>and</strong> explained the<br />
results on the basis of increased yield due to the increased weight<br />
of the endosperm of varietal crosses as compared with normally<br />
pollinated seeds within a variety.<br />
Other investigations have partially supported Carrier's contentions.<br />
Studies of the effect of pollen of a different strain or<br />
variety on endosperm development are given in Table XLVIII.<br />
TABLE XLVIII. IMMEDIATE EFFECT OF POLLINATION ON ENDOSPERM<br />
WEIGHT<br />
Number<br />
of<br />
tests
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