Tolerance of 254 Maize Doubled Haploid Lines × Tester Crosses to Drought at Flowering and Grain Filling

The doubled haploid lines (DHL) of maize in their top crosses are expected to include genotypes that accumulated favorable genes for both high-yielding and drought tolerance. The objectives of this study were: (i) to screen 254 DHL's x tester crosses for tolerance to water stress at flowering (WSF) and grain filling (WSG), (ii) to estimate the superiority of tolerant (T) over sensitive (S) crosses under WSF and WSG and (iii) to identify the selection criteria for drought tolerance in maize. Two hundred fifty four top crosses developed from crossing between 254 DHL's and an inbred tester along with two checks were evaluated under three watering treatments; i.e. well watering (WW), WSF and WSG using split plot design with two replicates. Based on drought tolerance index (DTI), maize genotypes (254 top crosses and 2 check cultivars) were grouped into three categories, namely tolerant (T), moderately tolerant (MT) and sensitive (S). The number of T, MT and S genotypes were 120, 108 and 28 under WSF and 123, 105 and 28 under WSG, respectively. The crosses classified amongst the drought tolerant and high yielding were No. 16, 14, 204, 96, 58, 140, 161, 2, 66 and 44 under WSF and No. 87, 96, 66, 208, 26, 153, 205, 177, 15 and 39 under WSG. Grain yield/ha (GYPH) of T was greater than that of S test crosses by 78.78 and 82.52% under WSF and WSG, respectively. DTI showed a significant (p≤0.01) and positive correlation coefficient (rg) with grain yield/plant (0.88 and 0.86), GYPH (0.82 and 0.80) and ears/plant (0.55 and 0.44) under WSF and WSG conditions, respectively. Moreover, DTI had small, but significant and negative correlation coefficients with days to anthesis, days to silking, anthesis silking interval, barren stalks and leaf rolling.