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Recombination of commercially available hybrids could produce desirable segregants that act as sources of new alleles for tomato breeding. Seven commercial single cross (SC) hybrids of tomato (Solanum lycopersicum L.) were crossed in a half diallel fashion to obtain 21 double cross hybrids (DC) to estimate combining ability, mode of gene action and extent of heterobeltiosis for fruit yield, processing qualities and tomato leaf curl virus (ToLCV) disease severity traits. Predominance of non-additive gene action occurred in the control for all characters except for total soluble solids (TSS) content in fruit that was conditioned by both additive and non-additive gene action. Improvement of most traits in DC hybrids over SC hybrids occurred. Maximum heterotic effect in DC hybrids was for vitamin C content followed by lycopene content, fruit yield per plant, titratable acidity content, number of fruit per plant and percent disease index of ToLCV. Two good combiners, 'PAN-1286' and 'Devi' among SC hybrids were identified based on general combining ability effects and average performance. Commercial exploitation of DC hybrids, 'TO-1458 × L-37' and 'NS-501 × TO-1458' following multilocational testing in the tropics and subtropics might be useful. High yielding, ToLCV disease tolerant DC hybrids could be exploited in segregating generations to identify elite multi-parent advanced generation inter-cross (MAGIC) populations. [ABSTRACT FROM AUTHOR]

Improvement of bitter gourd (Momordica charantia L.) has been constrained by a lack of adequate information on genetic control of fruit characteristics. Generation mean analysis was employed to understand the nature of gene action involved in conditioning of the fruit physico-chemical characters length, diameter, weight, total chlorophyll, β-carotene, and ascorbic acid contents, utilizing two contrasting crosses involving botanical varieties of bitter gourd. In both crosses, dominance, additive, and most of the epistatic components, were significant indicating a complex nature of inheritance for all characters under study. The dominance × dominance interaction effect was larger than the additive × additive effect. Duplicate epistasis in both crosses indicated hindrance in advancement through selection. Most characters are under control of non-additive gene action, and the magnitude of additive component was lower than dominance × dominance component; selection for most characters might be difficult. Dominance estimates indicated there would be less likelihood of isolating genotypes with fruit of increased size and having high β-carotene content from the crosses involving small-fruited M. charantia var. muricata Willd. as a parent because small fruit exhibited dominance. There would be a possibility of isolating genotype with fruit having high ascorbic acid content in segregating generations of these cross combinations. Selection for improvement of fruit physico-chemical characters should be delayed to later generations of segregating populations in bitter gourd. The modified bulk method of selection is recommended, in which selection is performed after attaining homozygosity for maximum heterozygous loci. [ABSTRACT FROM AUTHOR]

Cherry tomato [Solanum lycopersicum var. cerasiforme (Dunnal) A. Gray] has the potential for improvement through heterosis breeding, which can be further utilized for the development of desirable recombinants. However, genetic control of yield, fruit quality, and disease severity traits are not well known. Six phenotypically diverse parents were crossed in half-diallel mating design to determine the extent of heterobeltiosis, mode of gene action, combining ability effects, and dominance effects for 18 quantitative traits to produce information that could lead to the development of improved genotypes. The predictability ratio indicated an overwhelming response of non-additive gene action in controlling the expression of most traits studied. Based on general combining ability effects, and average performance, genitors '16/TOCVAR-1ʹ and '16/TOCVAR-3ʹ could be potential donor parents in breeding. Based on average performance, heterosis manifested, and specific combining ability effects, crosses '16/TOCVAR-1 × 16/TOCVAR-3ʹ and '16/TOCVAR-1 × 16/TOCVAR-4ʹ were best in respect to yield, nutritional quality, and level of field tolerance against leaf curl virus disease under tropical and sub-tropical conditions. Partial- to over-dominance reactions for the inheritance of fruit yield, and other economically important traits, reflect the genetic basis of heterosis. Commercially exploitable cherry tomato hybrids with high antioxidant activity, tolerance to leaf curl virus disease, could be developed with the involvement of a single parent tolerant to this disease. [ABSTRACT FROM AUTHOR]