Evaluation of mass selection for yield in corn as measured by random S₁ lines and their testcrosses

Author

Syrus Abd-Mishani

Date of Award

12-1976

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Plant, Soil and Environmental Sciences

Major Professor

L. M. Josephson

Committee Members

V. H. Reich, R. R. Shrode, R. A. McLean, F. L. Allen

Abstract

A mass selected com population (MS 13), and the parent variety Jellicorse (Je) were evaluated at Knoxville and Crossville using random S₁ lines per se and S₀ lines topcrossed to an unrelated single cross. The selected population (MS 13) had undergone thirteen generations of mass selection for ear com yield. S₁ lines and their testcrosses of MS 13 did not demonstrate statistically significant average yielding superiority over lines of Je at either Knoxville or Crossville, or the two locations combined. Both S₁ and testcross progenies of MS 13 were greater in yield than Je at Crossville (14.3 percent and 7.9 percent) where more favorable environmental conditions existed for the tests. Indications are that frequencies of favorable yield genes were greater in progenies of MS 13 than in corresponding progenies of Je. Differences are attributable to the effect of mass selection on the parent variety but the unfavorable conditions of the test locations did not allow the selected plants to express maximum yield potential. The top yielding S₁ and testcross progenies of the study came from the selected population. Correlations between S₁ and testcross yields for Je and MS 13 were + 0.40** and + 0.48**, respectively. Genotypes of MS 13 produced more ears/plant with greater nubbin weights, produced taller plants with higher ear placement, and produced more lodged plants. Genotypes of MS 13 flowered later but they produce grain having slightly less moisture at harvest than genotypes of Je. However, differences in all measured traits were not great and generally nonsignificant at the .05 level of probability. Variance estimates show that genetic variability among S₁'s exceeded that among testcrosses for most traits, as expected, and that S₁ and testcross progenies of Je had less genetic variability in yield and yield related traits than S₁ and testcross progenies of the corresponding MS 13. The results suggest that mass selection increased genetic variance and particularly additively genetic variance of MS 13 relative to Je. The significant yield variability in MS 13 genotypes indicates that continued yield improvement is possible in the selected population from further cycles of mass selection under favorable environmental conditions.

Recommended Citation

Abd-Mishani, Syrus, "Evaluation of mass selection for yield in corn as measured by random S₁ lines and their testcrosses. " PhD diss., University of Tennessee, 1976.
https://trace.tennessee.edu/utk_graddiss/7907