Physiological markers for drought tolerance in maize (Zea mays L.)

Most maize (Zea mays L.) in Mexico is cultivated under rainfed conditions with a high frequency of drought stress periods during silking, a stage which is very sensitive to water deficits. Since the effect of drought depends on the genotype, in this study we compared four maize lines (L6, L13, L14 and L16), which bad previously shown contrasting responses to osmotic stress in vitro. Two water regimes were imposed: watering (every 10 d) and drought stress (without irrigation from 48-97 d after planting). Variables measured were grain yield, soil moisture, hydric potential and their components in leaves and female inflorescence, photosynthetic rate, aboveground biomass, days to flowering, and leaf and young ear concentration of soluble sugars. Yield data were used to calculate the drought susceptibility index (DSI). Based on yield and DSL L14 and L16 behaved as tolerant lines to drought stress, while lines L6 and L13 were susceptible. Tolerant lines showed lower reductions in kernel number per plant, photosynthetic rate, and aboveground biomass production during drought. The variables tasseling-silking interval, female inflorescence turgor and sucrose gradient between leaf and female inflorescence were not associated with drought tolerance of the line.