Krishnamrutha et al., Biological Forum – An International Journal 15(6): 53-59(2023) 53 ISSN No. (Print): 0975-1130 ISSN No. (Online): 2249-3239 Genetic Variability and Character Association for Grain Yield and it’s Related Traits in South Indian Rice (Oryza sativa L.) Varieties Krishnamrutha T. Suresh 1 , S.V. Sai Prasad 2* , C.V. Sameer Kumar 1 and T. Ramesh 3 1 Department of Genetics and Plant Breeding, College of Agriculture, PJTSAU, Hyderabad (Telangana), India. 2 Department of Plant Breeding, ICAR-Indian Institute of Rice Research, Hyderabad (Telangana), India. 3 Department of Crop Physiology, College of Agriculture, PJTSAU, Hyderabad (Telangana), India. (Corresponding author: S.V. Sai Prasad*) (Received: 18 March 2023; Revised: 22 April 2023; Accepted: 21 May 2023; Published: 20 June 2023) (Published by Research Trend) ABSTRACT: With current trend in the population growth, the demand for food in most parts of the world is increasing year by year. However, variability in yield among the crop species may be exhausted sooner or later, limiting the potential for additional crop improvement. As a result, understanding the genetic diversity of crop species is crucial for any crop improvement programmes. Hence the present investigation was carried out at Indian Institute of Rice Research, Hyderabad during kharif 2022 with 96 rice lines to assess the genetic variability for yield and its attributing traits. Analysis of variance revealed highly significant differences for all the traits studied. The estimates of PCV were slightly higher than the corresponding GCV for days to 50% flowering, days to maturity, plant height, panicle length, number of grains/panicle, weight of grains/panicle, 1000 grain weight and SPAD indicating that direct selection can be practiced for these characters. High heritability with high genetic advance were recorded for days to 50% flowering, flag leaf length& width, number of grains/panicle, weight of grains/panicle, 1000 grain weight and SPAD before booting indicating predominance of additive gene action. Correlation studies revealed that, the grain yield/plot had a significant and positive association with number of productive tillers/meter (0.27), weight of grains/panicle (0.32), biomass/plot (0.93) and harvest index (0.40). Tocher's clustering approach was used to group all genotypes into 10 clusters in which, cluster II was found to be the largest with 47 genotypes. Keywords: Rice, Lattice design, Genetic variability, Correlation, Genetic diversity. INTRODUCTION Rice, commonly referred to as the “global grain” belongs to the family Poaceae, which is one of the few crop species endowed with the most genetic diversity. India is the second largest producer of rice next to China with an area of 46.38 m ha and production of 130.39 million tonnes with a productivity of 2809 kg/ha (Directorate of Economics and Statistics, 2022). The genetic improvement of rice for yield and yield contributing traits is an important criteria to meet the food demand of the growing population (Rao et al., 2021). As a result, the creation of genetic variability for improving yield and yield-attributing traits is a pre requisite in any crop improvement programme. A systematic evaluation and characterization of germplasm lines along with the released and pre- released cultivars, not only aids in the discovery of superior and genetically divergent genotypes, but also provides knowledge regarding the value of genetic resources. The genetic improvement of quantitative characteristics present in the crop species is determined by the heritability pattern as well as the kind and quantity of diversity contained in the current germplasm (Iraddi et al., 2013). The magnitude of variation due to heritable component is very important, because it will guide in the selection of parents for crop improvement (Dutta et al., 2013). Heritability estimates combined with genetic advances are usually more useful in predicting the gain under selection than heritability estimates alone. The success of a breeding program depends upon the quantum of genetic variability available for exploitation and the extent to which the desirable characters are heritable (Tiwari et al., 2011). Genetic metrics like genotypic coefficient of variation (GCV) and phenotypic coefficient of variation (PCV) can be used to detect the degree of variability in germplasm. Grain yield is a complex character, the knowledge of correlation between yield and yield component traits are of great importance in the selection of elite genotypes for breeding programmes (Dhavaleshvar et al., 2019). Correlation coefficient analysis reveals the component traits on which parental selection can be done for genetic yield enhancement (Immanuel et al., 2011). Correlation studies would give reliable data on the nature, size, and direction of selection, especially Biological Forum – An International Journal 15(6): 53-59(2023)