Heterosis and General Combining Ability Study on Heat Tolerant Tomato (<i>Lycopersicon esculentum</i> Mill)

Abstract

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 performanc...

Heterosis for Fruit Yield and Heat Tolerance Traits in Tomato (Lycopersicon Lycopersicum Mill.) Under Field Conditions

“…Among all the hybrids, only Tropimech × Petomech showed significant negative heterobeltiosis, indicating existing genetic variability for the traits. Similar results were reported by Yadav et al (2013), Enang et al (2015) and Khan and Jindal (2016).…”

“…Seven hybrids indicated positive heterosis over the better parent. Similar findings were reported by Amaefula et al (2014) and Enang et al (2015).…”

“…Significant variations among studied genotypes recorded for all traits indicating sufficient variability exists in the materials used for the study and also indicating possibility for selection of suitable breeding materials for heat tolerant tomato improvement under high temperature environments. Similar results were reported by Hazra and Ansary (2008), Kugblenu et al (2013), Islam et al (2014) and Enang et al (2015). df = Degrees of freedom, PHT = Plant height, DFPFL = Days to 50% flowering, NBPP = Number of branches per plant, NCPP = Number of clusters per plant, NFLPC = Number of flowers per cluster, NFLPP = Number of flowers per plant, NFRPC = Number of fruits per cluster and NFRPP = Number of fruits per plant.…”

“…Negative heterobeltiosis recorded for days to 50% flowering is desirable because of their breeding value for developing early flowering tomato hybrids which could escape heat stress. Patwary et al (2013), Enang et al (2015) and Welegama et al ISSN 2166-0379 2018 (2015) reported significant negative heterobeltiosis for days to 50% flowering.…”

“…They observed significant heterosis for plant height, days to 50% flowering, number of branches per plant, number of flowers per cluster, number of fruits per cluster, number of fruits per plant, fruit length, fruit diameter, percent fruit set, fruit weight and fruit yield per plant over the better parent. Enang et al (2015) observed heterobeltiosis for plant height, number of flower clusters, number of fruit per plant and number of leaves among hybrids for heat tolerant. Camejo et al (2005) reported that, the optimal temperatures required for tomato cultivation are between 25-30 o C during daytime and 20 o C during the dark period and an increase of 2-4 o C over the optimal temperature adversely affects gamete development and inhibits the ability of pollinated flowers to develop into fruits and thus reduced fruit yield and size (Peet et.…”