Parâmetros genéticos de caracteres fisiológicos em populações F2 de tomateiro submetidas à seca

Abstract

The tomato culture is susceptible to stress conditions due to water deficiency, showing the importance of advancing studies with the identification of genotypes with greater capacity to adapt to this abiotic condition. The objective of this study was to estimate the genetic parameters of physiological characters submitted to drought during the vegetative stage, verifying the F2 generation response of two crosses. The crosses used were named Crossing A (Access UTFPR_2016 x Commercial Hybrid) and Crossing B (UTFPR_2037 x Commercial Hybrid). Seeds of the genotypes used had been obtained from the self-fertilization of F1 plants in a protected environment. For each combination of crosses, the parents (P1 and P2) and the F1, F2, RC1F1 and RC2F1 generations were separately seeded. During the production of seedlings were used trays of expanded polystyrene of 128 cells with commercial substrate. Upon reaching 3 true leaves, the plants were transferred to plastic cups with a capacity of 750 mL containing soil mixture and aviary bed. The irrigation system used during the experiment was via standard drip irrigation (80% CC) until adequate development, under greenhouse conditions. Upon reaching the first expanded leaf, the plants were allocated in growth chamber in condition of 20% of the field capacity for 20 days. The mean temperature during this period was 25 °C and the relative humidity was 60%. Then, chlorophyll content, relative water content and proline concentration were evaluated. The results of the analyzes of each variable were used to estimate the genetic parameters of the F2 generation. The relative water content and Chlorophyll Index was higher for Cross-A, while the proline concentration was higher for Cross-B (39.48 μg mL-1). Heritability estimates in the broad sense were below 20% for all characters in Cross B and moderate to high in Crossing A. Only the proline concentration of Crossing A showed high heritability indices in the narrow sense. The results indicate that there is dominance occurrence for most of the characters, and early selection is not efficient.