Molecular Marker Application to Incorporate Salinity Tolerance to West Africa Rice Varieties.

Salinity is a serious constraint for rice production in West Africa. Molecular markers are now routinely being used to identify and transfer useful genes/QTLs for salinity tolerance. Our goal is to precisely transfer QTLs conferring salinity tolerance into popular African rice varieties to enable higher and more stable yields for farmers living off these marginal lands. One of the major QTL (Saltol) derived from the salt-tolerant Indian landrace Pokkali, has been mapped on chromosome 1. The map-based cloning of a gene providing salinity tolerance at the seedling stage (SKC1) in a similar position as Saltol in the cultivar Nona Bokra was previously published. The QTL for salt tolerance and SKC1, maintains K⁺ homoeostasis in the salt-tolerant cultivars under salt stress, and the SKC1 gene encodes a member of HKT-type transporters. The Africa Rice Centre aims to employ a marker-assisted backcrossing (MABC) approach to introgress Saltol into several African varieties that will subsequently be deployed for commercial cultivation.

 Fine-mapping of the Saltol QTL and the development of indel markers based on candidate genes in this region are being pursued at IRRI. MABC has been used to transfer the Pokkali Saltol QTL into popular varieties such as IR64, BR28, and BR11. A diverse set of germplasm including the upland and lowland NERICAs (New Rice for Africa), collection from Cassamance regions in Senegal and Gambia are also being characterized for physiological traits underlying salinity tolerance to identify new sources of tolerance for use as donors in breeding and for identification of novel QTLs. Besides, MABC is currently being used to introgress Saltol into few varieties popular in West Africa. The long term goal is to identify and combine genes and QTLs controlling different physiological mechanisms to achieve a higher level of salt tolerance in high yielding West African rice varieties.