Relation of seed weight to grain yields in oats, Avena sativa L.
SummaryWe measured yielding ability and weight per 100 seeds in 7 populations of oat lines, each derived from a different cross. The association between these two traits was curvilinear, with maximum yields occurring when 100-seed weights were between 2.75 and 3.10 g.In a simulated selection experiment conducted on a bulk population of 150 oat lines (i.e. only lines with seed weight between 2.75 and 3.10 g per 100 seeds were saved), the proportion of superior yielding lines was increased from 16% in the original to 32% in the new one. In the 100-seed weight class below 2.75 g, the proportion of high yielding lines was only 5%.
Mass selection for seed width in oat populations
Heterogeneous and segregating oat populations subjected to no selection and to mass selection for seed width for five consecutive generations were evaluated for 100-seed weight, heading date and plant height.The mass-selection technique, which consisted of passing the seeds over a screen with 12.7×2.4 mm slots and propagating the seeds too wide to go through the slots, was repeated for five consecutive generations (F3 through F7). Comparable unselected populations were grown each year. Remnant seeds from each check and mass-selected population were stored for future studies.In 1963, 500 random seeds from each of the six unselected populations (F2 through F7), from each of the five mass-selected populations (F3 through F7) and from a pure line were space-planted in the field. In 1964, the progenies from 75 random strains (a strain was the progeny of one spaced plant) from each of the 12 populations were sown in a randomized-block experiment with three replicates. In 1966, the strains from the last (F7) generation of the unselected and mass-selected lines of descent (75 strains from each) were tested for yield in a 7-replicate randomized block experiment.The mass-selection technique increased the mean 100-seed weight, whereas in the unselected line of descent, the mean 100-seed weight did not change. The mean heading dates became later and the mean plant heights taller with the mass-selection procedure. The mean yield of the final mass-selection population was nine percent higher than that of the comparable unselected population.In spite of the associated changes between 100-seed weight and plant height and heading date in successive generations; the genotypic correlations among strains within populations indicated that these three traits were inherited independently. In advanced generations (F6 and F7), the genotypic variances for heading date and 100-seed weight were reduced in both the unselected and mass-selected lines of descent, whereas, for plant height no significant change occurred in either.
An Evaluation of Effects of Mass Selection and Seed Irradiation With Thermal Neutrons on Yield of Corn 1
Although the irradiation treatment was detrimental to yield, the irradiated strain significantly outyielded the original variety and yielded only slightly less than the mass-selected control strain after four generations of selection. It is doubtful that irradiation of an already genetically variable population will prove to be particularly valuable as a breeding procedure; yet it is too early to draw definite conclusions. Additional generations of selection are needed. Because of its simplicity and apparent effectiveness, the use of mass selection of individual plants is suggested as a possible method of yield improvement in populations of corn segregating for genes controlling yield. Where the advantages of hybrids other than yield are desired, mass selection is suggested as a possible means of increasing the frequency of favorable genes in segregating populations prior to inbreeding. If over-dominance exists at any locus, mass selection will not be successful in altering gene frequency for that locus after an equilibrium point is reached. Some possible explanations are advanced for the apparent lack of success of early corn breeders using mass- selection and ear-to-row breeding techniques.