Diallel analysis of grain iron and zinc density in southern African-adapted maize inbreds

Iron and zinc deficiencies in humans are prevalent in areas where maize (Zea mays L.) constitutes a significant portion of the human diet, such as sub Saharan Africa. This study determined the breeding potential for increasing grain Fe and Zn density to increase Fe and Zn intakes among maize-consuming populations. Fourteen southern African-adapted white-grained maize inbred lines were crossed in a diallel. The F-1 hybrids made among seven high and seven low Fe and Zn concentration lines were evaluated in six locations, two replications per location, throughout Zimbabwe in 1999-2000. There were five high productivity sites and one low-N site, typical of the low-input production conditions of small-scale farmers in Zimbabwe. Grain Fe and Zn concentrations were analyzed with an inductively coupled argon plasma emission spectrometer. Variation among genotypes was highly significant for flour Fe and Zn concentration and per kernel Fe and Zn content. General combining ability (GCA) effects for flour Fe and Zn concentration were significantly more important than specific combining ability (SCA) effects in high yielding environments, indicating that per se line evaluation could identify promising lines. Under low N conditions, one low Fe-Zn parent line had a significant positive GCA effect for flour Fe concentration, with no effect on flour Zn concentration. In inbred trials, this line was among the low Fe-Zn lines, though in hybrid combination it emerged as a highly promising line. Therefore, test-cross performance and per se line evaluation should be used to identify iron- and zinc-rich materials for low-N environments.