Topcross pearl millet hybrids for Africa: A case study for Mali.

Single-cross pearl millet hybrids are widely grown in India, but this cultivar type has not been adopted in Africa. Hybrids from India have proven to be highly susceptible to downy mildew disease in Africa, the continent where the disease originated. We investigated an alternative strategy of growing topcross hybrids where both the parents are of African origin and both are only partially inbred. We investigated root characteristics – length, diameter, area, volume and dry weight – under drought stress and well-watered controlled conditions in genotypes that included potential parents of topcross hybrids. Several, including population Civarex 06_05, had better developed roots under drought while also having good roots under more favourable conditions. Some of these genotypes were backrossed to a male-sterile line based on the A₄ cytoplasm to produce male-sterile populations with stable male sterility. Civarex 06_05 had good combining ability when used as a female parent and produced high-yielding topcross hybrids. Two of the topcross hybrids were on restorer populations Toroniou, originating from Mali, and Maiwa from Nigeria. On the experimental station and in farmers' fields, one was much superior in yield to the best local alternatives and both had superior downy mildew resistance. Current efforts on the seed production of these topcross hybrids are described, and the constraints to the commercialisation in Mali of promising topcross hybrids are discussed. [ABSTRACT FROM AUTHOR]