Genetic Variability and Character Associations in Upland Rice (Oryza sativa L.) Genotypes Evaluated at Gojeb and Guraferda, Southwestern Ethiopia

Rice is an important cereal crop grown in different parts of Ethiopia.Despite information on genetic variability is a pre-requisite for further improvement of any crop, studies on genetic variability and association of charactersamong the rice genotypes in southwestern Ethiopia is very limited. Therefore, this research was conducted to estimate the extent of genetic variation and association among yield and yield related characters in upland rice genotypes. A total of 36 upland rice genotypes were evaluated for 18 characters using simple lattice design at two locations (Gojeb and Guraferda) during the 2017 main cropping season. The combined analysis of variance over the two locations revealed that the genotypes showed highly significant(P≤0.01) differences for all the characters studied, except for days to 50% heading, panicle weight, thousand seed weight, lodging incidences anddisease (leaf blast and brown spot). Similarly genotype × location interactions revealed highly significant (P≤0.01) differences for panicle shattering and grain yield and significant (P≤0.05) differences for days to 85% maturity, plant height, number of fertile tillers per plant, number of unfilled spikelets per panicle and biomass yield.Higher phenotypic coefficient of variation (PCV) and moderate genotypic coefficient of variation (GCV) were observed for panicle shattering.Moderate to high broad sense heritability was observed for days to 85% maturity, panicle length, number of total tillers per plant, number of fertile tillers per plant, number of filled spikelets per panicle, number of unfilled spikelets per panicle, biomass yield, harvest Index, number of panicles per meter square and plant height. Among the studied characters number of total tillers per plant, number of fertile tillers per plant, number of panicles per meter square, biomass yield and harvest Index had moderate values of genetic advances as percent of mean. Grain yield showed positive and highly significant correlations with days to 85% maturity, panicle length, number of fertile tillers per plant, number of panicles per meter square, biomass yield and harvest index at both genotypic and phenotypic levels. Phenotypically, number of panicles per meter square and genotypically, harvest index exerted the maximum positive direct effect on grain yield. The squared distance (D2 ) analysis grouped the 36 genotypes in to four clusters. This makes the genotypes become moderately divergent. The Chi-square (x 2 ) test showed that all inter-cluster squared distances was highly significant. The principal component analysis revealed that four principal components have accounted for 70.54% of the total variation. The present study revealed that number of panicles per meter square and harvest index can be considered for selection. However, there was no sufficient genetic variation for the characters studied in the rice genotypes therefore,it is better to widen the genetic base of the rice genotypes by hybridization and introduction of more rice germplasms from International Rice Research Institute and African Rice Center for a successful breeding program in Southwestern Ethiopia. In addition, in order to give confirmative results, further studies in more locations and years, supported with molecular breeding approach should be conducted on rice genetic variability and character association.