Progress in Delivering Drought Tolerant Maize to Farmers in Southern Africa.

Maize is the most important staple food in southern Africa with human maize consumption averaging 91 kg per capita per year. Current maize yield averages 1.2 t ha^-1 and is barely sufficient for the region’s requirements.  To contribute to improved production CIMMYT initiated a Drought Tolerant Maize for Africa (DTMA) project in 2006, targeting mid-altitude areas of the region. Varieties were selected in Zimbabwe using simultaneous selection in three types of environments; (i) recommended agronomic management/high rainfall conditions, (ii) low N stress, and (iii) managed drought. Between 2010 and 2012, 40 elite drought tolerant maize hybrids and open pollinated varieties (OPVs) developed and selected by the DTMA project  were compared with with the best commercial checks and farmer-preferred varieties across 70 locations in Zimbabwe under farmers’ conditions. However analysis was later narrowed to 13 varieties that were common across seasons. The trials were grouped into five categories using trial means ranging from 0-1 t ha^-1 to above 4 t ha^-1. Within these categories the varieties were grouped according to maturity groups -that is early and medium to late maturing groups. Results showed that the varieties were significantly different (P≤0.001) in the 3-4 t ha^-1   and above 4 t ha^-1  categories, while  no significant differences were observed in the 1-2 t ha^-1  and 2-3 t ha^-1  categories. The new drought tolerant hybrids showed a yield advantage over the commercial check varieties both in the early and medium-late maturing categories. The relative yield advantage ranged from 6-18%. Combined analysis of variance for additive main effects and multiplicative interaction (AMMI)showed significant differences (P≤0.05) for G x E interaction thereby indicating opportunities to select for stability amongst the genotypes. The two AMMI IPCAs explained 80.7% of the variation, and they were significant (P≤0.001) and P (≤0.05) respectively. The results showed both narrow and broad adaptability, with CZH0616 showing narrow adaptation and CKH08210 showing broad adaptability respectively.