Prediction of F1 progeny variation in tomato (Solanum Lycopersicum L.) from parental divergence assessed by SSR markers

Abstract

Background: Although the use of heterosis is one of the most significant achievements of agriculture, the genetic mechanisms of this phenomenon still remain unclear. Development of numerous molecular tools stimulated efforts to determine the prognostic criteria for selection of best parental combinations. In result of studying the relationship between heterosis in F1 and genetic divergence of the parents, the prospects of utilizing DNA markers have not been persuasively established due to inconsistent findings. Materials and methods: Molecular-genetic data have been used to predict heterosis in F1 hybrids of tomato. Estimates of the genetic dissimilarity of parents for all pair-wise combinations of testcross (4 × 6) were performed based on patterns of 11 SSR informative markers (PIC 0.28-0.85). The general (GCA) and specific (SCA) combining ability of line, mid-parent heterosis (MPH) and high-parent heterosis (HPH) of F1 were assessed. Relationship between GD, MPH and HPH were calculated by correlation analysis. Result: The level of total SSR divergence of the parental lines was significantly associated with heterosis and SCA (sij) for fruit weight and fruit number per plant. Notably, the highest values of MPH and HPH were obtained in the most divergent pair-wise combinations. Lowest negative values of heterosis were observed in the F1 progeny from the least divergent lines. But the main group of F1 progeny demonstrates wide variation of heterosis due to SSR GD have low prognostic potential. Conclusion: Estimation of GDs may be useful for predicting promising combinations, but has limitations, since only a part of F1 heterotic advantage may be explained by the genetic divergence of its parents. Probably for understanding and manipulating heterosis the genetic divergence must be dissected to select “positive” markers, i. e. those that allow identifying the part of heterogeneity associated with the expression of heterosis in F1.