The authors evaluated 57 parental inbred lines of maize hybrids disseminated in Southwest China for drought tolerance under drought-stressed and well-watered conditions.Multiple regression analyses between drought tolerant coefficients Of the grain yield per plant and 15 morphological and physiological traits measured from a subset of 12 selected lines, identified traits 1 and 5,which were important for drought tolerance,at the seedling and reproductive stages respectively.Gene effects,combining abilities,and heritabilities of these traits were estimated using generation mean and diallel cross methods.Dominance effect was more important than additive effect for the plant height,anthesis-silking interval(ASI),root weight,and the grain yield per plant,whereas,they were about equal for the leaf emergence rate.The variances of special combining ability(SCA)were about double that of the general combining ability(GCA)for plant height,ASI and grain yield per plant,although they were about equal for leaf emergence rate and root weight.Narrow sense heritabilities 0f the five traits for the reproductive stage were not high(12.8-29.6%),although broad sense heritabilities for plant height,ASI,and grain yield were as high as 70-85%.A segregating population consisting of 183 F2 plants from the cross N87-1 (drought tolerant)×9526(susceptible),was genotyped at 103 SSR loci and me F2:4 families were evaluated under two water regimes.Twelve quantitative trait loci(QTLs)(two for plant height,five for ASI,four for root biomass,and one for grain yield)were identified,most of which had overdominant gene action.Some chromosomal regions,such as those linked to markers umc1051(bin 4.08),umc2881(bin 4.03),and phi034(bin 7.02),had overlapping QTLs.