RICE Germplasm Development for Blast Disease, Cold Tolerance and Salt Affected Environments: Progress MADE in Breeding and Genetic Analysis at Africa RICE Center.

Rice production in Africa is affected by many biotic (blast, BLB, RYMV) and abiotic stresses (salinity, drought, heat and cold) which threaten the sustainability of rice production among farmers.

Tolerance to most of this stresses are controlled by a complex of characters resulting from the interaction of many quantitative component traits. Marker-based genetic studies have permitted the identification of reliable QTLs for many abiotic and biotic stresses. To demonstrate the value of marker-aided selection to manipulate QTLs, we described some examples of introgression of genes/QTLs for blast, cold and salinity tolerance into elite Africa germplasms (Sahel 108, RASSI, Kogoni-90-1, BG90-2 and NERICA-L-19). For blast resistance, 2 resistant genes (Pb1 and pi21) which have been reported to have broad spectrum of resistance under field conditions from 2 varieties; MODAN (Pb1) and Owarihatamochi (pi 21) were introgressed into popular Africa varieties through backcrossing with selection based on marker information alone. The evaluation of BC2F2 families has also been conducted under field conditions. For cold tolerance, we used a cold-tolerance QTL (qCTB8) from donor “Suito ChuukanBohon Nou 11 and introgressed into Africa popular varieties using only the marker information. In targeting both cold tolerance (qCTB8) and salinity tolerance QTLs (Saltol), two 2 and 3 cycles of backcrosses with selection based on marker information and field evaluation were conducted. The BC3F4s and BC3F5s for salinity tolerance have been characterized for other agronomic performance under field conditions; whilst for the cold, agronomic characterization is been conducted on the BC2F3 families. These approaches show that much progress can be made by combining both markers selection and evaluation under the stress condition after each cycle of hybridization. In addition we shall demonstrate the development of high yielding rice varieties by AfricaRice which are been disseminated in Africa through the Africa-Wide Rice Breeding Taskforce systems. The long term goals are to develop a higher level of tolerance to cold, salinity and blast in high yielding African rice varieties.