Breeding Values of 254 Maize (Zea mays L.) Doubled Haploid Lines under Drought Conditions at Flowering and Grain Filling

Breeding value is the main parameter of initial screening through top cross analysis as it represents the general combining ability (GCA) effects of individual test line. Two hundred fifty four top crosses were produced as a result of crossing between 254 doubled haploid lines (DHL) developed by inducer technique and the inbred line tester PHDMF. The main objective was to identify the DHL's of high breeding value under drought at flowering and grain filling to be exploited in a breeding program aiming at developing drought tolerant maize hybrids. A split plot design in lattice (16 x 16) arrangement was used with two replications, where three irrigation treatments (well watering; WW, water stress at flowering; WSF and water stress at grain filling; WSG) were allotted to main plots and genotypes (254 top crosses) to sub-plots. A separate analysis of variance of RCBD was also performed under each irrigation treatment. Results suggested the existence of significant (p≤ 0.01) differences among studied DHL's × tester crosses under respective irrigation treatments for all studied traits. For each of the ten studied traits, number of desirable DH lines for GCA effects was identified under WSF and WSG conditions. For grain yield/ha (GYPH), number of desirable DH lines for further exploitation in breeding programs; i.e. those having positive and significant GCA effects was 66 for drought tolerance at flowering and 82 for drought tolerance at grain filling. The best ten DHL's in GCA effects for GYPH were No. 16, 204, 44, 66, 62, 2, 14, 161, 76 and 160 under WSF and 66, 208, 87, 15, 26, 205, 39, 177, 102 and 153 under WSG conditions. It was observed that for a given trait, the rank of doubled haploid lines for GCA effects was the same rank of their top crosses for mean performance.