Genetic Diversity Of Some Rice (Oryza Sativa L.) Landraces Grown In Tanzania Using Simple Sequence Repeat (SSR)

ABSTRACT

Simple sequence repeat (SSR) microsatellite markers were used to analyze genetic variation of 70 samples of Rice (Oryza sativa L.) Landraces grown in Tanzania. The objective of the study was to assess the extent of genetic variation in traditional rice varieties and establish their genetic relationships for developing breeding strategies. Ten (10) SSR markers were found to be polymorphic with a minimum of 1 and a maximum of 6 alleles. Variability in the number of alleles was obtained with an average of 4.9 alleles per locus. The genetic analyses were carried out using the NTSYs pc (Version 2.02) Software and a cluster diagram constructed base on genetic distances detected between landraces by the UPGMA method. Results showed a large amount of variability within Oryza sativa species. The overall pattern of variation as well as the degree of relatedness among accessions is shown in the dendograms generated from similarities or genetic distance matrices. Rice landraces Lifumba, Tunduru and Dunduli ya mlimani had wider genetic base with distant coefficient range of 0.66-0.98. It is advocated to include them in the National Rice Improvement Programme in Tanzania. Some landraces had narrow genetic base range of 0.76-0.98 distant coefficient. Rice landraces Katumahi Simzito, Tuliani and Afaa Kikangaga, were found to be genetically distant at 0.98 coefficient and can be used for intended breeding purposes. The reaction of landraces to RYMV infection was evaluated using three strains of the virus. The tested strains were S4 ex Kyela, S6 ex Mang'ula, and S6 ex Dakawa. Most of landraces were susceptible to RYMV. However, only a few landraces expressed high levels of resistance to all three strains, characterized by lack of symptoms until harvest.