On-Farm Yield Gains with Stress Tolerant Maize for Eastern and Southern Africa.

Drought and low nitrogen (N) stress are two of the major causes associated with low maize yields and high year-to-year yield variability in sub-Saharan Africa. Throughout history plant breeding has played a key role in increasing yields and productivity. Genetic gains in maize breeding in Eastern and Southern Africa under experimental conditions over the past 10 years were recently estimated at 1.4%, 0.85%, 0.85%, and 0.62% per year for optimal, managed drought, random drought, and low N stress conditions, respectively. The relative yield gap between controlled condition on experimental stations and farmers’ field is probably higher in SSA than anywhere else in the world and can be attributed to the multiple stresses crops face throughout the season in smallholder farmers’ fields. While testing in controlled environment is essential to attain high heritability and selection pressure, it is essential to ensure new varieties for commercialization perform in the environment which matters the most, the farmers’ fields. The aim of this study was to compare new hybrids and OPVs against the best commercial varieties in ESA under farmer management to validate on-station results. A total of 50 trials were conducted in farmers’ fields in Ethiopia, Kenya, Tanzania, Malawi, Mozambique, Zambia and Zimbabwe over a two-year period. Under low yielding conditions (1-2 t ha-1) new varieties out yielded current commercial varieties by up to 0.5 t ha-1. In high yielding conditions (>=3t t ha-1) the yield gap was narrow between new and commercial varieties suggesting increased yield stability of new varieties did not reduce yield potential. The analysis of variance for additive main effects and multiplicative interaction (AMMI) across the two seasons showed significant differences (P?0.05) for G x E interaction thereby indicating opportunities to select for stability amongst the genotypes.