Quality assessment of rice genotypes involves physicochemical and sensory test. A physicochemical test relies on the rice chemical composition, cooking quality, gelatinization temperature and physical properties of cooked rice. The aim of this study was to determine the physicochemical characteristics of selected Kenyan and Tanzanian genotypes based on gel consistency and alkali digestion. Diverse classes of rice exist with different expression levels of gel consistency and alkali digestion. As these traits are major contributors to the eating and cooking quality traits, unscrupulous traders mix both low and high-grade rice hence making enormous profits from their sales. Minitab 17.0 software package was used to determine the means and the standard error of means of the gel consistency physicochemical test results while the alkali digestion values were determined based on the standard evaluation system by International Rice Research Institute. Majority of the genotypes had high alkali digestion. Based on the gel consistency test, the average GC values ranged from 31.50 mm in ITA 310 to 99.5 mm in IR 2793. Genotype BS 217 showed significant difference from Kilombero, IR 64, Kahogo, Saro 5, ITA 310, IR 54, Wahiwahi and BW 196. These results show that physicochemical characterization using the available test procedures can be effectively utilized in analysis of diversity in rice germplasm

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Rice (Oryza sativa L.) is the main staple food for more than half of the world's population. Improving cooking and eating quality of rice is one of the important objectives of many plant breeding programs. Aroma and cooked kernel elongation are two critical parameters that determine the market value, cooking and eating qualities of rice. The objective of this study was to evaluate the genetic diversity of thirteen (13) Oryza sativa L. populations from Kenyan and Tanzanian. Genetic diversity was determined using 8 simple sequence repeats (SSR) markers. Diversity data was analyzed using POWERMARKER version 3.25 and GENALEX v 6.5 software packages. The number of alleles per locus ranged from 2 to 4 alleles with an average of 3.12 across 8 loci. The polymorphic information content (pic) ranged from 0.2920 (RM 282) to 0.6409 (RM 339) in all loci with an average of 0.4821. Pair-wise genetic dissimilarity coefficients ranged from 0.1125 to 0.9003 with an average of 0.5312. The average gene diversity over all SSR loci for the 13 rice varieties was 0.6036, ranging from 0.3550 to 0.6391. Maximum genetic similarity was observed between Kilombero and Supa, BS 370 and BS 217. Minimum genetic similarity was observed between Kahogo and BS 217. Cluster analysis was used to group varieties by constructing dendrograms based on SSR data and morphological characterization of grains. The dendrogram based on SSR data formed two distinct clusters of the 13 rice varieties. RM 339 and RM 241 were the most informative markers and could be used for differentiating rice varieties from diverse geographical origins. Results obtained from this study demonstrated that use of trait specific SSR markers can be relied upon in diversity studies among diverse and closely related genotypes. RM 339 and RM 241 markers are recommended for use in diversity studies and in quality assurance for grading of rice varieties. Further analysis should be carried out using a larger number of samples and markers to come up a more conclusive report on the discriminating power of microsatellite markers based on rice grain quality traits.

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