Heterosis and combining ability for maize adaptation to tropical acid soils: Implications for future breeding strategies
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Soil acidity reduces maize (Zea mays L.) yields by up to 70% on 8 million hectares in developing countries. Several breeding programs have produced populations better adapted to these conditions. The objectives of this study were to evaluate these populations for both per se cultivation and the development of new breeding germplasm. To do so, we generated a diallel cross design, which included six acid soil-tolerant and five susceptible populations with high yield potential or tolerance to other stresses. Populations and crosses were evaluated in five environments, on acidic Al-toxic soils and in comparable limed soils in Guadeloupe, Cameroon, and Colombia. Soil acidity decreased grain yield by 46 to 73%, depending on the location and year. Significant genotype X soil condition interactions were observed for grain yield. Mid-parent heterosis for yield was significantly higher in acid soils (32%) than in nonacid soils (20%). This suggests that the development of variety crosses between acid soil-tolerant populations could be used to increase maize yields in acid-soil cropping systems. The observed high general combining ability (GCA) for yield variation of the crosses in acid soil and its close relationship to per se performance suggest that parental populations of variety crosses could be efficiently screened on the basis of per se performance in acid soil.
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