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Comparison of Selection for S 2 Progeny vs. Testcross Performance for Population Improvement in Maize
Author(s) -
Horner E. S.,
Magloire E.,
Morera J. A.
Publication year - 1989
Publication title -
crop science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.76
H-Index - 147
eISSN - 1435-0653
pISSN - 0011-183X
DOI - 10.2135/cropsci1989.0011183x002900040005x
Subject(s) - biology , inbreeding depression , overdominance , selection (genetic algorithm) , inbreeding , population , selfing , inbred strain , linear regression , zea mays , zoology , statistics , mathematics , agronomy , genetics , demography , gene , allele , artificial intelligence , sociology , computer science
Several methods of population improvement in maize ( Zea mays L.) are available, but more information is needed to enable breeders to make the best choice among them. This study was conducted to compare selection among S 2 progenies (S 2 method) with selection based on testcross performance using inbred testers (TC method) in two populations, FS8A and FS8B. For the TC method, a line from FS8A was the tester used to evaluate S 2 lines from FS8B and vice versa. Four cycles of selection were completed, and the selected populations were evaluated over a 4‐yr period. Testing was done at two locations near Gainesville, FL, during both the selection and the evaluation phases. Gains in average combining ability over both populations and all tests were 4.7 and 3.0% cycle −1 for the TC and S 2 methods, respectively (significantly different at P = 0.01). Linear regression based on these mean values accounted for 99% of the variation among cycles for each method. The TC method also produced higher predicted yields of populations per se ( F = 0) in Cycle 4 (6.85 vs. 6.01 Mg ha −1 ). On the other hand, the S 2 method resulted in a lower rate of yield depression in Cycle 4 for each 1% increase in inbreeding (0.04 vs. 0.06 Mg ha − ) and in higher predicted yields of inbred ( F = 1) populations (1.70 vs. 0.87 Mg ha −1 ). These results suggest that nonadditive gene action in the overdominance range is important in these populations because, in the absence of overdominance, the S 2 method is expected to be the better procedure.