Abstract

Low pH in soils is attributed as the main contributor to the low yields characteristic in maize production regions of Angola. Here, eight white-kernel acid soil tolerant donor lines (ASTDLs) sourced from CIMMYT-Colombia (testers) were crossed with eight white elite lines adapted to the mid-altitude climatic conditions from CIMMYT-Zimbabwe, in order to identify donor lines, which can be potential sources of acid tolerance genes in breeding programmes in Angola. The two groups of parents were crossed using a line by tester (L×T) mating design, yielding 47 crosses with sufficient seed, which were evaluated alongside eight acid tolerant commercial hybrids, during the 2014-16 cropping seasons at nine sites, representing acid and non-acid soils in Angola and Zimbabwe. Effects of general combining ability (GCA) due to lines and testers, as well as specific combining ability (SCA) on grain yield were significant (P < 0.05) under acid soils. From the CIMMYT-Zimbabwe breeding programme, inbred lines identified as ZW1, ZW4 and ZW5 together with the CIMMYT-Colombia ASTDLs (i.e., CW4 and CW8) seemed to be ideal parents for crosses that can do well under both the acid and non-acid soils. The best specific cross for acid soils was identified as ZW1 × CW8 (CH142512), whereas for non-acid soils, ZW3 × CW4 (CH142500) was identified. Interestingly, the cross ZW1 × CW8 was also observed as stable under both acid and non-acid soil conditions. Overall, data showed potential of exotic acid tolerance donor lines for enhancing low-pH adaptation in sub-tropical maize populations.

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