The assessment of genetic diversity of the traditional rice varieties or landraces is an essential component in germplasm characterization and conservation to identify potential parents. In the present study SSR markers (588 SSR markers) were used for the assessment of genetic diversity and relatedness among 31 rice accessions. These included 18 accessions from Sudan and 13 from IRRI. Among the SSR markers used only 483 generated polymorphic patterns, and showed 1274 alleles. The number of alleles per locus ranged from 2 (about 214 markers) to 5 (RM16820 and AP3206a) with an average of 2.64 alleles per locus. The polymorphic information content (PIC) values ranged from 0.06 (RM3138, RM10671, SKC3, R1M7, R6M30, S07101 and S12041B) to 0.69 (RM7643), with an average of 0.39. The major allele frequency per locus varied from 32% (RM7643) to 97% (RM3138, RM10671, SKC3, R1M7, R6M30, S07101 and S12041B), with an average of 64%. Among the primers used in the present investigation, RM7643 was highly informative as it recorded the highest PIC value (0.69). The UPGMA resulted in allelic richness of four major clusters in which cluster I is composed of a high number of accessions. The pairwise genetic dissimilarity indices revealed the highest genetic dissimilarity of 62.3% between Pipanfary Red1 and FL478. The lowest genetic dissimilarity was found between NBGS3 and NBGS2 (4.1%), but they showed wide dissimilarity with other accessions. The study highlighted the usefulness of the application markers for efficient characterization of the Sudanese rice accessions.
Morpho-physiological and genetic studies of salinity are important in understanding the mechanism of plant adaptation to stressful environment. Eighteen rice genotypes collected from Sudan and South Sudan, which were never tested for salt tolerance, as well as two genotypes (FL478 as tolerant check and IR29 as sensitive check) from the International Rice Research Institute (IRRI), were subjected to salinity stress at seedling stage. Test was carried out in hydroponic system applying electrical conductivity (EC) 12 dS/m NaCl using randomized complete block design with three replicates. Most of the genotypes showed sensitivity to salt stress; one genotype PIPANFARY RED2 was moderately sensitive and three genotypes MASURY1, MASURY2 and FL478 were tolerant. Salinity significantly reduced leaf dry weight, shoot dry weight, root dry weigh and biomass production (biomass/plant) by 31%, 42%, 60% and 47%, respectively. Tolerant genotypes accumulated low amount (2.52 g/100 g dry weight (dwt)) of Na + in the root, whereas highly sensitive genotypes accumulated high amount (3.87 g/100 g dwt) of Na + . Tolerant genotypes showed less reduction in K + concentration than the sensitive genotypes. Therefore, they maintained lowest Na + /K + ratio in the shoot (1.47%) than in the root (3.69%) compared to the intolerant genotypes (7.49% and 8.49%). The genotypes that showed tolerance to salinity stress can be used as a source of resistance/tolerance in a breeding program for rice improvement in uplands areas in semi-arid condition.
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