GENOTYPE X ENVIRONMENT INTERACTION AND MOLECULAR DIVERSITY STUDIES OF SELECTED RICE (Oryza sativa L.) GENOTYPES ACROSS THREE NIGERIAN AGRO-ECOLOGICAL ZONES

Abstract

The use of same variety across different major ecological zones needs to be reviewed for optimum productivity therefore; six exotic and ten Nigerian elite rice genotypes were evaluated for stability and molecular diversity in Okitipupa, Akure and Akungba in Ondo State, South-West, Nigeria. The rice genotypes were collected from Malaysia and Africa Rice, Ibadan, Oyo State. They were planted in the rainy seasons of 2013, 2014 and 2015 in three locations which represent the three agro-ecological zones of Ondo State to evaluate their yield performance, stability and genetic variation. The genotypes were also characterized using SSR markers and their chemical qualities determined with particular focus on amylose content, gel consistency and gelatinization temperature/Alkali spreading value. The field experiment was laid out in a randomized complete block design (RCBD) replicated three times. Data were collected on yield and yield component traits and the results analyzed statistically using Generalized Linear Model (GLM) of SAS version 9.0 for the analysis of variance, the variance components, phenotypic and genotypic coefficients of variation, heritability, genetic advance and expected genetic gain were also estimated. Factor Analysis (FA), Principal Component Analysis (PCA) and Cluster Analysis were employed to analyze the magnitude and pattern of diversity among the rice genotypes. Stability and performance of the genotypes were evaluated using Finlay-Wilkinson, AMMI and GGE biplot procedures. The first five factors from FA captured 79.3% of the total variation while the first eight PCA accounted for 93.1% of the total variation. Both tools identified plant height, panicle weight, panicle length, number of grains per panicle, one thousand grain weight and grain yield in discriminating the rice genotypes. Faro 57 was identified as the most stable genotype with BW 348-1 and IRRI 154 as the bests performing genotypes across the three locations. Genotypes G7, G10 and G15 were adapted to Akungba whereas G9 and G6 were adapted to Akure and Okitipupa environments. GGE biplot models showed that the five environments belong to a single mega-environment. Molecular diversity studies using microsatellite markers generated UPGMA dendrogram which grouped the selected genotypes into four distinct clusters and primer RM 29 assisted in the identification of the rice genotype that could be selected for hybridization purposes by showing heterozygosity due to the presence of double bands in some of the genotypes. The chemical quality tests on amylose contents, gel consistency, gelatinization temperature/alkali spreading value suggested that Faro 57, Faro 44 and WITA 4 would be preferred by consumers for good cooking and eating qualities. The study focused mainly on stability and molecular diversity studies. Selection of high yielding genotypes could be based on high broad sense heritability estimates of the yield component traits. The influence of genotype x environment interactions helps in the partitioning of the effects of GEI as a pre-requisite for stability in crop improvement. The microsatellite markers revealed the degree of similarity among selected rice genotypes. The cooking and eating quality of rice genotypes gave information on the AC, GC and ASV/GT for consumer to make choices.