Line x tester analysis for combining ability, heterosis, and genetic parameters in tomato yield and fruit quality traits

Abstract

Tomato (Solanum lycopersicum L.) yield in Ghana remains low ( ~7.5 t ha-1), far below the >40 t ha-1 potential of improved hybrids, due to limited adapted varieties, bacterial wilt, tomato yellow leaf curl virus, and poor shelf life under high ambient temperatures. The objective of this study was to evaluate the combining abilities, heterotic patterns, and gene action governing yield and climate-resilient fruit quality traits in a diverse set of tomato germplasm. Five parental genotypes comprising three lines and two testers were crossed in a 3 × 2 line × tester mating design to develop six F1 hybrids. Parents, hybrids, and the commercial check Shasta were evaluated in a randomised complete block design, with three replications across the major and minor cropping seasons of 2022 at CSIR-Crops Research Institute, Kwadaso, Ghana. Nine traits were measured namely; plant height, fruits per plant, fruit yield, fruit weight, total soluble solids, pericarp thickness, number of locules, number of seeds per fruit, and shelf life. Pooled analysis of variance showed significant differences among lines and testers for most traits; while genotype × environment interactions were non-significant, indicating short-term temporal stability at Kwadaso. General combining ability variance exceeded specific combining ability variance for yield, fruits per plant, fruit weight, and seeds per fruit, with Baker’s predictability ratio >0.8, suggesting predominance of additive gene action. WV009 had significant positive GCA for yield (4.22) and fruits per plant (3.30); while CRI-PHE had positive GCA for fruit weight (9.65**). The hybrid CRI-PHE × WV009 showed significant positive standard heterosis for yield (151.3%) and mid-parent heterosis for fruits per plant (56.5%), but also significant negative better-parent heterosis for shelf life (-44.7%), revealing a yield × shelf-life trade-off. High narrow-sense heritability (83.6%), coupled with high genetic advance as a percentage of mean (71.1%) was observed for yield. Results indicate that pedigree selection and pure-line extraction from segregating F2 populations will be effective for yield improvement in this material. Hybrid CRI-PHE × WV009 is recommended for yield maximisation but requires backcrossing with shelf-life donors before commercial deployment. Traits such as total soluble solids with low genetic advance may need introgression from wild relatives for improvement.