Gene action studies of biochemical traits in tomato under open field and protected conditions

The goal of the current study was to understand the type and extent of gene action for different biochemical traits in tomato. Fourteen diverse lines of tomato were crossed in diallel fashion (excluding reciprocals) and tested for gene action investigations in two environments viz., open field and polyhouse. The analysis of variance revealed significant mean squares for all the traits under both the environments. The additive variance was higher than the dominance variance for most of the quality traits among all the crosses in both the environments. The gene action studies revealed greater magnitude of dominance component than additive component demonstrating greater role of dominance component in the inheritance of traits studied. The net dominance effect component showed absence of significantly high dominance effect in heterozygote and absence of directional dominance for all such traits. However, for total soluble sugars (TS) and lycopene content (Lyc) in both environments; total carotenoids content (Caro) and proline content (Pro) in E₁, significantly high dominance effect in heterozygote and presence of directional dominance was observe. The F value indicated higher frequency of dominant alleles in the parents for traits viz., ascorbic acid content (AA), Lyc and Caro in both the environments; TS and titratable acidity (TA) in E₂. The average degree of dominance [(H₁/D)^1/2] revealed over dominance range for all the traits under study in both the environments. The estimates of H₂/4H₁ (the proportion of genes with positive and negative effects on the parents) indicated the asymmetrical distribution of alleles with positive and negative effect in the parents for all the traits. The estimates of KD/KR (number of dominant and recessive genes in parents) revealed excess of dominant genes in parents as compared to the recessive genes. The estimates of h²/H₂ (number of gene groups controlling that character and exhibiting dominance) depicted the less proportion of dominance gene groups for major traits however, for TS and Lyc in E₂ and indicated higher proportion of dominance gene groups. The estimates of h² (heritability n.s.) revealed that the genes were showing non-additive gene action for most of the traits in present set of material. The study highlights the importance of both additive and non-additive gene action involved in the inheritance of biochemical traits.