Electronic Journal of Plant Breeding, 8(2): 509-520 (June 2017) ISSN 0975-928X http://ejplantbreeding.com 509 DOI: 10.5958/0975-928X.2017.00077.1 Research Article Genetic studies in tomato for yield and its components under high temperature Reecha T. Das * , Pranab Talukdar and Akashi Sarma Department of Plant Breeding and Genetics, Assam Agricultural University, Jorhat 785013, India E-mail: das.reecha@gmail.com (Received: 21 Nov 2015; Revised: 04 April 2017; Accepted: 21 April 2017) Abstract Generation mean analysis was carried out on six generations (P 1 , P 2 , F 1 , F 2 , B 1 and B 2 ) in four tomato crosses viz. Cross-I (H7997 x CLN 1621 E), Cross- II (H7997 x BL 337), Cross - III (H7997 x Nagcarlan) and Cross- IV (H997 x CLN 2366A). Observstions were recorded on eight yield attributing characters including yield. The presence of epistasis was recorded in all the four crosses. From six parameter model regression of the components of six parameter model on environmental indices it was evident that it was evident that additive effect played a decisive role in the inheritance of number of primary branches per plant, number of fruiting clusters per plant and fruit yield per plant. Dominance effect was found significant and consistent in one or more crosses for days to flowering, number of fruiting clusters per plant and fruit yield per plant. Duplicate epistasis was more predominant for most of the characters in the crosses. Key words Tomato, gene action, heat tolerance, yield Introduction Tomato (Lycopersicon esculentum Mill.) belongs to the family solanaceae and it is native of Peru, Equador region (Rick, 1965). In many countries it is known as poor man’s orange (Dhall and Singh, 2013) because of its attractive and nutritive value. High temperatures during the growing season have been reported to be detrimental to growth, reproductive development and yield of several crops (Singh et al., 2007). Development of tomato cultivars with improved fruit set under high temperature would be valuable for tomato crop production in regions where the temperature during part of the growing season reaches ≥ 35°C or higher (Johnson and Hall, 1953). Progress in developing heat-tolerant cultivars has been hindered by the complexity of the trait and its low heritability values (Villareal and Lai, 1979). To develop heat tolerant varieties the information on the nature of gene action controlling the economic characters is considered important. Knowledge of genetic architecture of the characters under improvement is essential for adopting appropriate breeding procedure. Such knowledge leads the breeder to develop new commercial varieties of the crop. Study of inheritance of the characters would facilitate the adoption of appropriate breeding strategies and improve efficiency of selection procedure. Material and Methods The experiment was conducted at three different environments during offseason and one in rabi season, 2012-2013 at the Experimental Farm, Department of Horticulture, Assam Agricultural University, Jorhat, Assam, India. The farm is situated at 26°44´ N latitude and 94°l0´E longitude with elevation of 9l m above mean sea level. The weekly data obtained from the Department of Agricultural Meteorology, Assam Agricultural University, Jorhat, Assam, Indian on monthly mean maximum and minimum day temperatures during the period of investigation showed that mean maximum ranged from 21.90 – 44.00 O C and mean minimum temperature ranged from 9.50 to 30.00 O C. Four heat tolerant tomato genotypes viz., CLN 1621E, BL 337, Nagcarlan and CLN 2366A, and one heat sensitive genotype H 7997 were utilised to generate four crosses. viz. Cross-I (H7997 x CLN 1621 E), Cross- II (H7997 x BL 337), Cross - III (H7997 x Nagcarlan) and Cross- IV (H997 x CLN 2366A) by attempting crosses during rabi, 2012 and these along with the parental lines H7997, CLN 1621 E, BL 337, Nagcarlan and CLN 2366A comprised the entries for experiment on generation mean analysis. H7997 was used as a recurrent parent in backcross I (B 1 ) and the heat tolerant genotypes were used as recurrent parent in backcross II (B 2 ). Two rows of each parent, F 1 and backcross generations and eight rows of each F 2 were planted in randomized block design with two replications. Inter and intra row was kept as 50 cm and 30 cm respectively. Observations were recorded on five randomly selected plants in each of P 1 , P 2 , 10 plants of F 1 and 40 plants in F 2 and 20 plants that of B 1 and B 2 in each of the replications on days to first flowering, days to fruit maturity, number of primary branches per plant, days from flowering to fruit setting, flower shed percentage, number of fruiting clusters per plant, number of fruits per plant and fruit yield per plant. Six generations of each of the three crosses were screened in four planting dates viz., 5 th March (E 1 ), 10 th April (E 2 ),