Plant Genome IV Conference Plant Genome IV Conference
Lepidopteran insects and drought are two of the more important causes of maize losses in developing countries. For example, it has been estimated that 30 out of 55 million hectares planted to maize in developing countries are seriously affected by insect problems. Drought has been estimated to result in nearly 20% yield loss on average, with losses over 50% common in many environments. In order to assist the breeding programs in improving tropical maize germplasm for insect resistance and drought tolerance, molecular markers are being used to first identify genomic segments which could be transferred to susceptible varieties to improve these two traits. Methods employed to detect putative QTL range from simple single-factor analysis to maximum-likelihood methods such as employed in MapMaker-QTL. More recently, composite interval mapping has been used to further refine the locations of QTL in our studies. Molecular and QTL maps for resistance to two tropical borers and the anthesis-silking interval have been developed using F2 and RIL populations. Marker-assisted backcrossing programs are underway for both traits to transfer the mapped genomic regions from resistant/tolerant inbred lines to susceptible varieties. In the case of drought, cycles of selection are being fingerprinted to determine if allelic shifts have occurred at the ASI loci detected in the mapping phase. Results and progress for these two important traits in maize will be presented and discussed in relation to the feasibility to use molecular markers for improving maize germplasm.