Abstract
Soil acidity has received less attention than other biophysical stresses such as drought and low N, despite accounting for a considerable reduction in maize (Zea mays L.) productivity in many parts of southern Africa. The line × tester mating design was used to determine the general combining ability (GCA) for grain yield of 14 maize inbred lines and the specific combining ability (SCA) of their corresponding crosses. Thirty‐three single‐cross hybrids were evaluated under acid and optimum soils across 11 environments over three seasons. Across environments, mean grain yield reduction ranged from 11 to 37% due to low pH. Additive gene action was more important than nonadditive gene action for grain yield under both soil conditions. Tester GCA effects were larger for grain yield than GCA effects of lines and SCA effects of crosses for both soil conditions. Tester GCA effects were less sensitive to environmental fluctuations than line GCA effects and SCA effects of crosses. Cross combinations with desirable SCA effects for grain yield were associated with high per se grain yield, which suggests that SCA was a good predictor of grain yield in this study. These crosses consisted of good × good and good × poor general combiners, which indicates that GCA was a good predictor of grain yield. Therefore, priority should be given for yield selection in progenies and hybridization of specific crosses with desirable SCA when breeding acid‐soil‐tolerant maize.
Highlights
Maize (Zea mays L.) is grown and consumed in various forms as a major staple food and source of proteins and calories by millions of people in Southern Africa (Smale, Byerlee, & Jayne, 2011)
Parts of southern Africa such as Zimbabwe is threatened by acid-soil-induced nutrient deficiency and heavy metal intoxication (Dhliwayo et al, 1999; Nyamangara & Mpofu, 1996)
Three acid-soil-tolerant inbred lines from the International Maize and Wheat Improvement Center (CIMMYT)’s acid soil breeding program in Colombia were used as testers crossed with 11 lines from the Department of Research and Specialist Services (DR&SS) and CIMMYT–Southern Africa Regional office (SARO) to generate 33 single-cross hybrids
Summary
Maize (Zea mays L.) is grown and consumed in various forms as a major staple food and source of proteins and calories by millions of people in Southern Africa (Smale, Byerlee, & Jayne, 2011). Parts of southern Africa such as Zimbabwe is threatened by acid-soil-induced nutrient deficiency and heavy metal intoxication (Dhliwayo et al, 1999; Nyamangara & Mpofu, 1996). Low soil pH can lead to Al, Mn, or Fe toxicities (Tandzi et al, 2015; Tandzi, Mutengwa, Ngonkeu, & Gracen, 2018). Acid-soil toxicity in plants is caused by a combination of heavy metal intoxication, deficiency of essential nutrients, and acidity per se (Bian, Zhou, Sun, & Li, 2013; Tandzi, Mutengwa, Ngonkeu, & Gracen, 2018). An increase in the proportion of acidic soils leads to potential crop production problems such as low fertilizer use efficiency, Al toxicity, P unavailability, and micronutrient deficiency, and increased susceptibility to drought, which severely reduces maize yields (Bian et al, 2013).
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