Comparative performance of top-cross maize hybrids under managed drought stress and variable rainfed environments.

Drought occurs at high frequency in maize production zones in Africa. Carefully controlled moisture deficits have been imposed at anthesis and grain filling stages of maize to develop drought tolerant germplasm. The present study was conducted to examine the potential effects of drought tolerant parents selected under such managed drought stress on agronomic performance of their top-cross hybrids across variable growing conditions in the rainy season. Three independent trials consisting of top-cross hybrids involving drought tolerant parents and commercial hybrids were evaluated under manged drought stress (MDS) and well watered (WW) condition at Ikenne in Nigeria for 3 years during the dry season and across 30 stressful (SE) and 52 favourable (FE) rainfed environments in West Africa. The drought stress imposed in the dry season caused a 53-64 % annual average yield reductions in these trials. In spite of these, about 56 % of the top-crosses produced high grain yields under MDS and WW conditions. The rank orders for hybrid grain yields did not change markedly across different years under MDS and WW conditions. Also, nearly 78 % of the top-crosses produced high grain yields across SE and FE environments in the rainy season. Sixteen top-cross hybrids amongst these were present in the top yielding groups under the MDS environment. Some high yielding top-crosses with stable performance across variable rainfed environments were identified in the current study. The phenotypic and genetic correlations between grain yield under MDS and that under SE environment were positive and moderate. Also, the phenotypic and genetic correlations showed that the capacity of top-cross hybrids to produce high grain yields under MDS was independent of the yield potential under FE environment. These results suggest that selection of parents under manged drought stress promotes the development of top-cross hybrids broadly adapted to variable rainfed conditions. [ABSTRACT FROM AUTHOR]