Abstract
The choice of an appropriate tester is important for success in resistance hybrid breeding programs. Limited information is available on the most suitable testers that allow the selection of yellow endosperm maize inbred lines with good combining ability for resistance to witchweed (Striga hermonthica) and superior agronomic performance in hybrids targeted to areas infested with the parasite. Testcrosses of 30 Striga-resistant yellow endosperm maize inbred lines with three testers having varying levels of resistance to S. hermonthica were evaluated at Abuja and Mokwa in Nigeria under Striga-infested and non-infested conditions in 2018 and 2019. The lines × tester interaction was significant for grain yield under Striga infestation, indicating that the performance lines in testcrosses varied with the testers. The respective average general combining ability effect of lines and testers was 1.5 and 32.4 times greater than the corresponding specific combining ability effects under infestation, showing the greater importance of additive gene action controlling the performance of testcrosses under Striga infestation. The different testers exhibited a different capacity to discriminate among the test lines with the susceptible tester being the least effective. Most of the criteria used to determine the best tester favored the selection of the tolerant and resistant testers as promising candidates to identify superior Striga-resistant yellow endosperm inbred lines for the hybridization and development of resistant hybrids. The results of this study demonstrated that testers with a high frequency of desirable alleles were superior to the tester with a low frequency of favorable alleles in hybrid breeding programs for resistance to S. hermonthica.
Highlights
More than 90% of maize (Zea mays L.) produced globally is yellow, whereas more than 90% of the total maize produced in Africa is white [1]
The general combining ability (GCA) effects due to lines and testers were significant (p < 0.01) for all traits except anthesis–silking interval and ears per plant for lines, indicating that the additive genetic effects were important in controlling most of the traits
10 weeks after planting (WAP), indicating that the non-additive genetic effects were less important in controlling most traits measured in this trial
Summary
More than 90% of maize (Zea mays L.) produced globally is yellow, whereas more than 90% of the total maize produced in Africa is white [1]. Fato et al [40] found that a tester with a high frequency of favorable alleles for resistance to downy mildew (DM) disease in maize was better than a susceptible tester in discriminating inbred lines in terms of resistance to the disease under infection, days to anthesis and silking and grain yield. These authors, recommended the need for further studies to include more potential testers to improve breeding efficiency in resistance hybrid maize breeding program in Mozambique. The present study was, conducted to determine the effectiveness of yellow endosperm maize inbred line testers with diverse reactions to S. hermonthica for identifying lines with a high expression of resistance to the parasite in hybrid combinations
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