Herança de progênies F2 de tomateiros submetidas à deficiência hídrica

Abstract

Tomate production is undergoing transformations resulting from the modernization and the increase of sharp productivity. With the advent of the production of hybrid cultivars, farmers end up suffering from high seed costs and increasing dependence on the market. The tomato is susceptible to several conditions of abiotic stress, especially the drought, making it necessary to identify genotypes with greater capacity to adapt to this extreme condition. In addition, there are few reports in the literature on the heritability and estimation of the genetic parameters of the physiological and morphological characters in response to drought, which can serve as a basis for breeding programs aimed at better crop adaptation. Thus, the study aimed to analyzed the response to drought of the F2 generation, of parents and backcrosses, from two crosses, in order to estimate the genetic parameters of morphological and physiological characters in the vegetative stage. In the first year there were two crosses between parental combinations to obtain the F1 progenies, which originated in the second year the F2 seeds and the first backcross generation (P1 x F1) and (P2 x F1). For each combination of crossings, the parents were separately seeded (P1 and P2), F1, F2, and RC1F1 RC2F1. From this, the chlorophyll content, proline concentration, dry and fresh matter of shoots and roots, plant height, stomatal density and relative water content in the leaves of populations submitted to water deficiency were estimated for a period of 20 days. From these data for each variable were estimated genetic parameters obtained in the F2 generation from two different crosses. The mean values of fresh and dry matter of shoot were higher for Crossing 2 (3.62 and 1.52 g). On the other hand, the fresh and dry matter of root and root/shoot ratio were higher at Crossing 1 (0.63, 0.32 and 0.39 g). The proline concentration was higher for Crossing 1 (39.48 μg ml-1). Heritability values were moderate to high (over 20%) for most of the morphological characters at both crosses. All physiological characters presented broad-sense heritability for (below 20) at Crossing 1 and moderate to high at Crossing 2. The results indicate that for most of the morphological characters, the additive factor (fixable) contributes in large part to the variation of F2, indicating selection efficiency genotypes tolerant to water stress in early generations while the physiological characters present dominance to most of the characters not being efficient in early selection.