Evaluation of Genetic Variability, Trait Association, and Regression Analysis among Rice (Oryza sativa L.) Genotypes under the Agro-Climatic Conditions of Tando Jam, Sindh, Pakistan

Abstract

Rice (Oryza sativa L.) is one of the most important cereal crops worldwide, and the identification of superior genotypes based on agronomic traits is essential for developing high-yielding cultivars. The present study was conducted to assess genetic variability, trait association, and regression among twenty-five rice genotypes under field conditions using a randomized complete block design with three replications. Significant differences among genotypes were observed for most of the evaluated traits, indicating substantial genetic variability. Correlation and regression analyses were performed to determine the relationships among flowering, maturity, yield, and yield-contributing traits. Days to 50% flowering exhibited a very strong positive correlation with days to maturity (r = 0.998), whereas negative associations were observed with sterile spikelets and panicle length. The number of fertile spikelets showed significant positive correlations with tiller number, plant height, panicle length, and grain yield, while sterile spikelets were negatively associated with grain yield. Panicle length and plant height also exhibited positive relationships with grain yield, suggesting their importance as indirect selection criteria for yield improvement. The coefficient of determination indicated that flowering time explained approximately 99.6% of the variation in maturity. Overall, the findings demonstrate considerable genetic diversity among the evaluated rice genotypes and highlight fertile spikelets, panicle length, and plant height as key traits for selection in rice breeding programs aimed at improving productivity under the agro-climatic conditions of Sindh, Pakistan.