Determining the combinability of greenhouse orange bell pepper (Capsicum annuum L.) lines in terms of fruit characteristics

Objective
A significant proportion of vegetable hybrid seeds in the country are imported. By 2010,  this dependency on foreign sources was anticipated to  be reduced through domestic hybrid seed production. A fundamental requirement for any plant breeding and hybrid seed production program is the selection of suitable parents, and insights into the gene action controlling various traits. Diallel crosses are a useful method for identifying potential hybrid combinations and obtaining information on heritability, types of gene action, and predicting offspring performance.
Materials and Methods
A one-way diallel crossing scheme was conducted to evaluate the combining ability of seven orange bell pepper lines derived from six generations of self-pollination. The resulting 21 hybrids, and the seven parental lines, were cultivated in a randomized complete block design with three replications. In each replication, 10 plants per treatment (hybrid or parent) were grown in a greenhouse, totaling 30 plants per genotype. Traits were recorded throughout the growth period, including fruit length and diameter, flesh thickness, pedicel thickness, average fruit weight, and total fruit yield.
Results
Analysis of variance revealed that the differences among genotypes (parents and hybrids) were significant at the 1% probability level for all traits studied. Subsequently, Griffing’s method II was used to partition the genotype sum of squares into general combining ability (GCA) and specific combining ability (SCA) and to assess the nature of gene action. GCA and SCA variances were significant across all traits, indicating the involvement of additive and non-additive genetic effects. However, non-additive gene effects had a greater influence, as evidenced by Baker's ratio values below 0.5. The low GCA-to-SCA variance ratios further supported the predominant role of non-additive effects (dominance or epistasis) in trait expression.
Conclusion
Hybrids 31×20, 30×25, and 33×30 are recommended for DUS (Distinctness, Uniformity, and Stability) testing and potential cultivar release due to their high yield, desirable agronomic traits, and competitive performance against commercial hybrid controls.