Estimation of Gene Action and Genetic Parameters for Morphological Traits in F1, F2 and F3 Generations of Tomato (Lycopersicum esculantum L.)

Tomato is the second most important vegetables, after potato, which has the highest area of cultivation worldwide. Acording to FAO statistics, Iran is the sixth producer of tomato cultivation in the world. However, more than 95 percent of vegetable seeds are imported into the country. The present study was conducted in order to evaluate commercial imported hybrids (8320, Eden, Matin and Xaman) and the F2 and F3 generations resulting from their self-breeding. In this regard, after the production of F2 and F3 generations, three generations (F1, F2 and F3) together with the control variety (Early Orbana y) were evaluated in the research farm of Seed and Plant Improvement Institute, Karaj, Iran, based on a randomized complete block design with four replications during 2019-2020. The analysis of variance showed that the difference among genotypes for single plant yield, days to flowering, average single fruit weight, number of fruits harvested and acidity (pH), was significant at the level of 1% probability and total soluble solids (TSS) was significant at the level of 5%. The results of the mean comparison showed that the highest mean of single plant yield belonged to 8320 F1 (10920/10g), the highest days to flowering was observed in Xaman F2 (47.01 days), the highest mean weight of single fruit was observed in Xaman F1 (115.50 g), the highest number of fruits harvested was in Xaman F1 (106.62), the highest amount of total soluble solids was in Matin F3 generation (4.96) and the lowest amount of acidity (pH) was in 8320 F1 (4.10). The results of estimating genetic parameters showed that most of the evaluated traits had high genetic and phenotypic variances, but a slight difference was observed between the coefficient of phototypic variation and the coefficient of genotypic variation, which indicates a small effect of environment on the control of these traits. Higher variance of dominance than additive variance in most traits caused the degree of dominance to be greater than one, Therefore, the possibility of control of traits by genes with dominance or over-dominance effects is high, and in order to improve these traits, the methods for hybrid development are suggested.