Azarian Journal of Agriculture Azarian J. Agric. VOL (6) ISSUE 6, 2019: 153-163 http://dx.doi.org/10.29252/azarinj.020 www.azarianjournals.ir Azarian Journals Research article ISSN:2383-4420 351 Estimation of combining ability, heterosis, heritability, and generation mean in basmati rice (Oryza sativa L.) by line x tester design Ujjawal Kumar Singh Kushwaha *1, 3 , Indra Deo 1 , Prabha Shankar Shukla 1 , Dinesh Chandra Baskheti 1 and Anand Kumar Tewari 2 Article Info ABSTRACT Accepted: 29 Jan. 2020 Genetic parameters help to identify the breeding behavior of plants and aids in the selection of elite genotypes for hybridization programs. To determine the nature and type of gene action, to select superior genotypes and best cross combinations, combining ability, heterosis, heritability and five generation mean were estimated based on three susceptible varieties as lines and three resistant genotypes as testers in 2016. The three lines and testers were Pant Basmati-1, Pant Basmati-2, and Pant Basmati-17 and, BBL-180-5-1-4-1, Oryza perennis and improved Pusa Basmati-1 respectively. They were crossed in line x tester mating fashion. The plant progenies were grown up to three seasons to get P1, P2, F1, F2, and F3 to find out five generation mean. The experimental trial showed that all genotypes were significant and showed maximum variations among the traits. The general and specific combining ability values of lines and testers were also significant which prerequisite need for selection of superior genotypes. Maximum heterosis was reported in Pant Basmati-2 x Oryza perennis followed by Pant Basmati-2 x BBL-180-5-1-4-1 and Pant Basmati-1 x Oryza perennis respectively. The Highest heritability was recorded for 100-grain weight and lowest for days to flowering in all crosses. Five generation mean analysis showed epistatic non- allelic gene interactions like dominance and additive x additive gene interactions respectively. The overall results suggested that the selected lines, testers and cross Pant Basmati-2 x Oryza perennis were most appropriate for creating maximum heterosis which showed non-allelic gene interactions. Keywords: Combining ability, Five generation Mean, Genetic parameters, Heritability, Heterosis INTRODUCTION 1 rops are good gift of nature, ultimately utilized by human being for the benefit of mankind. Mendel’s discovery revealed the facts that crop traits are determined by certain phenomena known as heredity. The study of heredity and its mechanism thus help to understand and develop crops of interest. Scientists are able to predict genetic parameters of edible food crops and hence hundreds of improved varieties and hybrid are now available globally (Yang and Hwa 2008). 1-Department of Genetics and Plant Breeding, College of Agriculture, G. B. Pant University of Agriculture and Technology, Pantnagar-263145, India 2-Department of Plant Pathology, College of Agriculture, G. B. Pant University of Agriculture and Technology, Pantnagar- 263145, India 3-Agriculture Botany Division, Nepal Agricultural Research Council, Khumaltar, Lalitpur, Nepal * E-mail: kushujjwal@gmail.com Genetic parameters like combining ability, generation mean, heterosis and heritability are the fundamental biometrical tools used mostly for forecasting the breeding behavior of plants. Their estimation is prerequisite pre-breeding statistical procedure to select superior genotypes as parents and develop them as a variety. To predict the suitable genotypes as a parents, combining ability and heritability could help as a wonderful tools if the crossing materials are novel (Singh et al. 2019, Bagheri et al. 2008). Heterosis is the superiority of first generation (F1) over its parents that compares the novel hybrid with their competitors. It is popularly used for comparing different hybrids. Heritability determines the heritable nature of traits and number of genes transferred from parents to its offspring. It depicts the percent of traits transfer from parents to next generations. Combining ability like general and specific combining ability determine the degree and direction of cross among C