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. These landraces were Afaa Mzinga
Lingwelingweli, Mbega, Jambo twende, Kalibumbula, Msonga, Mzinga, Lunyuki,
and Tosa can be used for breeding purposes.
