Heterosis and General Combining Ability Study on Heat Tolerant Tomato (Lycopersicon esculentum Mill)

Abstract

A study was carried out to estimate heterosis and general combining ability on heat tolerant tomato ( Lycopersicon escullentum Mill). The experiment was conducted at the Teaching and Research Farm of Department of Crop Production and Horticulture Modibbo Adama University of Technology, Yola. (latitude 9o18′N) gene action governing inheritance of characters in tomato ( Lycopersicon escullentum Mill) under high temperature stress. The experiment was conducted at the Teaching and Research Farm of Department of Crop Production and Horticulture Modibbo Adama University of Technology, Yola. (latitude 9o 18'N and long 12o 15'E) and the Teaching and Research Farm of Adamawa State University, Mubi (latitude 10o 03'N and long. 13o 07'E) all in Adamawa state of Nigeria. Fourteen entries consisting of six parents and eight crosses developed by crossing two males (testers) and four females (lines) following line x tester design were evaluated in three replications in a Randomized Complete Block Design (RCBD) in two locations. Ten plants where randomly sampled for recorded observation. Data were collected from the following characters; trichome count, plant height at 60DAT, number of leaves per plant at 60DAT, number of fruits per plant, weight of fruits per plant % damaged fruits and number of days to final harvest. Data were subjected to biometrical analysis. Result of the analysis of variance indicated highly significant difference for all characters among entries except weight of fruits per plant. The result suggested the presence of genetic variability among the tomato genotypes under study. Significant difference were observed in the combining ability analysis of variance in all the agronomic characters under study except for trichome count suggesting both additive and non-additive genetic effects were important in governing this characters under study with more preponderance of additive effects. The cultivars, Cherry, Currant, UC28B and RomaVF were identified as the best general combiners and the best yielders in terms of number of fruits per plant with appreciable tolerance to heat damage. N and long 12o 15′E) and the Teaching and Research Farm of Adamawa State University, Mubi (latitude 10o 03′N and long. 13o 07′E) all in Adamawa state of Nigeria. Fourteen entries consisting of six parents and eight crosses developed by crossing two males (testers) and four females (lines) following line x tester design were evaluated in a Randomized Complete Block Design (RCBD) with three replications. Ten plants where randomly sampled for recorded observation. Data were collected on Trichome count, plant height at 60DAT, number of leaves per plant at 60DAT, number of fruits per plant, weight of fruits per plant % damaged fruits and number of days to final harvest. Data were subjected to biometrical analysis. Result of the analysis of variance indicated highly significant difference for all characters among entries except weight of fruits per plant. The result suggested the presence of genetic variability among the tomato genotypes under study. Significant difference were observed in the combining ability analysis of variance in all the agronomic characters under study except for trichome count suggesting both additive and non-additive genetic effects were important in governing this characters under study with more preponderance of additive effects. The cultivars, Cherry, Currant, UC28B, and RomaVF were identified as the best general combiners and the best yielders in terms of number of fruits per plant with appreciable tolerance to heat damage. However, Currant x Roma vf and Cherry x Golden roma exhibited some level of heterosis in number of leaves, number of flower clusters, number of fruits per plant and plant height. Cherry and Currant, though identified as having highest performance in all characters under study are not commercially acceptable but could be utilized in breeding programs for improvement of tomatoes with required agronomic characteristics. However, UC28B, Roma vf and Golden roma are genotypes that have shown greater performances in all the agronomic characters which could be used for commercial cultivation. Furthermore, Currant x Roma vf and Cherry x Golden roma are desirable segregates that can be used to develop improved tomatoes with required agronomic characteristics through recurrent selection by backcrossing.