| Summary: | Salinity significantly reduces global rice yield, especially in Eastern and Southern Africa, necessitating the development of salinity-tolerant varieties. We collected and analyzed 201 rice varieties, including Tanzanian landraces. Using 1k-RiCA SNP markers, we found that 36 out of 201 genotypes possessed the Saltol allele, a marker for salinity tolerance. Only two genotypes, K5 and Intsindagira bigega, were both phenotypically tolerant and had the Saltol allele. Interestingly, 16 genotypes without Saltol showed salinity tolerance, suggesting other salinity tolerance QTLs. The distribution of Saltol and phenotypically tolerant genotypes varied across Tanzanian agro-ecological zones, with the Coastal Zone showing a higher proportion of tolerant genotypes, possibly due to farmer selection pressure. However, ancestral population proportion correlated with decreased salinity tolerance. This study highlights the complex relationship between environmental factors and population structure in shaping the genetic and phenotypic composition of landraces. The identified tolerant genotypes could be utilized in breeding for new salinity-tolerant-rice varieties
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