Rank Comparisons of Unadapted Maize Populations by Testers and Per Se Evaluation
- B. C. Abel and
- L. M. Pollak
Evaluation of the many unadapted maize (Zea mays L.) accessions in the world's gene banks is a monumental task. This study compared rankings of unadapted accessions testcrossed to eight testers with their per se performance as sources of favorable genes that enhance grain yield and other traits. Testers included the populations BS13 and BS26, the single crosses B14 ✕ B37 and Oh43 ✕ Mo17, and the inbreds B37, B14, Oh43, and Mo17. The accessions were a diverse array of 34 populations collected from Yugoslavia. The 272 testcrosses and the 34 accessions per se were evaluated in a series of randomized complete-block designs, with each block containing a set of either testcrosses within each tester or the accessions per se. Field experiments were conducted at three Iowa locations for 3 yr (1985–1987). Significant variation among testcrosses or accessions occurred within sets for grain yield, grain moisture, root lodging, stalk lodging, days to anthesis, plant height, and ear height. Testcrosses with B14 ✕ B37, B14, Oh43, and Mo17 did not interact with environments for grain yield. Testcrosses with B14 and Mo17 had the least root lodging, and those with B14 ✕ B37 and B14 had the least stalk lodging. Testers ranked some accessions somewhat similarly for grain yield, but extreme differences in ranking by different testers also occurred. The most extreme differences occurred comparing Oh43 with Mo17 and B14 ✕ B37 with Oh43 ✕ Mo17. Ranking of accessions per se for grain yield was different from ranking via testers. Rankings of accessions for other traits were similar for testers and per se evaluation. Due to differential ranking among testers and per se evaluation for grain yield, it is suggested that more than one tester be used to screen unadapted maize accessions. That tester should also exhibit a high frequency of favorable alleles for traits such as root and stalk lodging, to allow easier data collection.
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