Gains from improvement for mid-season drought tolerance in tropical maize ( Zea mays L.)

Abstract

Drought and low soil fertility are major factors limiting maize production in the tropics. We examined the performance of hybrid progenies of drought-tolerant populations (DTP) in stressed (drought and low-N) and unstressed environments. A set of high-yielding normal single cross hybrids, developed using inbred lines improved with main emphasis on yield per se under optimal input conditions, was evaluated and compared with DTP c9 S 3 topcrosses across environments. Performance of normal hybrids was slightly better than DTP-topcrosses under unstressed conditions. However, under stress normal hybrids performed poorly with an average yield of 3.3–4.8% under drought and 34.8–36.2% under low-N stress. Hybrid progenies from DTP yielded up to 31.8–42.4% under drought and 48.9–63.6% under low-N as compared with their yields with out stress. Estimation of gains with selection for mid-season drought stress in DTPs over selection for improved yields under optimal input conditions showed that the gains were remarkable for drought (89.6%), and also for low-N stress (39.3%). The improved performance of DTP hybrids across environments was due to improvements in secondary traits such as reduced anthesis–silking interval, increased ears per plant, delayed senescence and relatively high leaf chlorophyll during late grain filling. Correlations between the performance of genotypes under drought and low-N stresses were positive and fairly high for DTP progenies, both white ( r 2=0.45 ∗,r=0.56 ∗ ) and yellow ( r 2=0.42 ∗,r=0.52 ∗ ), while it was not significant with normal hybrids. Selection for mid-season drought tolerance resulted in morpho-physiological changes that proved advantageous under both drought and low-N stress, without significant yield penalties under optimal input conditions.