Plant Genome III Conference Plant Genome III Conference
Drought ranks as the second most severe limitation, after soil infertility, to maize production in less developed countries. Drought stress just before or during the flowering period, causes a delay in silking that can be measured as an increase in the length of the anthesis-silking interval (ASI). Selection for reduced ASI in tropical open-pollinated varieties appears to be correlated with improved yields under drought stress. While the heritability of ASI seems to be relatively high, selection for reduced ASI is best achieved under specific drought conditions, which severely limits its use in many breeding programs. Therefore, molecular markers were used to identify genomic segments responsible for ASI with a view towards their use in marker-assisted selection. An F2 population of 260 individuals was genotyped for 140 loci. The F2:3 families were evaluated in the field under severe and intermediate stress levels for ASI, a number of morphological traits, and several physiological drought parameters. Five QTLs (LOD scores greater than 2.5) were identified for ASI on chromosomes 1, 2, 6, 9 and 10; together, these account for approximately 60% of the genetic variation in silk delay. Results of the analysis of other traits measured in the population will be presented in detail and implications for use in marker assisted selection discussed.