QTL analysis of drought related traits and grain yield in relation to genetic variation for leaf abscisic acid concentration in field-grown maize

Abscisic acid (ABA) concentration is a quantitatively inherited trait which plays a pivotal role in the response of plants to drought stress. A recent study identified 17 quantitative trait loci (QTLs) controlling bulk-leaf A BA concentration (L-ABA) in a maize (Zea mays L.) population of 80 F, rando m families tested for two years under droughted field conditions, Sixteen o f the QTL regions influencing L-ABA also harboured QTLs for one or more of the following traits: stomatal conductance, a drought sensitivity index, le af temperature, leaf relative water content, anthesis-silking interval, and grain yield. The analysis of the effects of each QTL region on the investi gated traits indicated that L-ABA mainly represented an indicator of the le vel of drought stress experienced by the plant at the time of sampling beca use an increase in L-ABA was most commonly associated with a decrease in bo th stomatal conductance and grain yield as well as an increase in leaf temp erature. Opposite results were observed at one QTL region on chromosome 7 n ear the RFLP locus asg8. A model is presented to interpret these contrastin g results in terms of pleiotropic effects.