Seleção de linhagem-elite de meloeiro gália resistente à mosca minadora por meio de caracteres agronômicos

Abstract

The leafminer (Liriomyza sativae) is the main pest of melon plants in the Northeast region, which accounts for 96% of the Brazilian melon production. Its larvae cause damage to the leaf mesophyll, reducing photosynthates and consequently compromising fruit production and quality. Thun, obtaining hybrids resistant to the leafminer has become one of the objectives of the Melon Breeding Program at Embrapa (MBPE). Thus, starting from the resistant line BAGMEL 56R, through the Backcross Breeding Method, the introgression of resistance (Ls allele) into elite breeding lines of MBPE was initiated, aiming to obtain resistant elite breeding lines. In this context, the objective of this work is to select the descendant elite breeding line most similar to the recurrent parent (G1.S) based on the genetic similarity between the original elite breeding line and the descendant elite breeding lines resistant to the leafminer, through agronomic evaluation of production and fruits. The experiment was conducted at the Experimental Field of Pacajus, at Embrapa Agroindústria Tropical. Eleven descendant resistant elite breeding lines and the recurrent elite breeding line were evaluated. The resistant donor parent was included only as a standard for resistance evaluation. The experimental design was randomized complete blocks with three replications and nine plants per plot. In the field, in addition to resistance to the leafminer itself, production variables (number of rejected and commercial fruits, weight of rejected and commercial fruits, total number and weight of fruits, percentage of commercial fruits and fruit weight, number and weight of commercial fruits per plant, total number and weight of fruits per plant, average weight of commercial fruits, and average weight of all fruits, and productivity) were evaluated. Futhermore, three fruits per plot were selected for evaluation of quality parameters (skin and flesh color and aroma; skin and flesh thickness; number of locules; fruit abscission; fruit weight, length, and width; internal cavity diameter; firmness, soluble solids, titratable acidity, and SS/TA ratio). Analysis of variance, mean comparison using Dunnett's test, and multivariate analyses were performed: Principal Component Analysis for characterization and hierarchical clustering (UPGMA) and Tocher Optimization for grouping. Dunnett's test showed no statistical differences between the descendant elite breeding lines and the original elite breeding line. Both Principal Component Analysis and Tocher Optimization indicated that the lines closest to the recurrent parent were A3.8, A2.1, and A5.6. Using the hierarchical method, the resistant elite breeding lines A3.8, A5.6, A2.1, and A1.3 were the closest to the G1.S genotype. The variables that contributed the most to the dispersion were the number and weight of commercial fruits. Therefore, the descendant elite breeding lines showed broad similarity to the recurrent parent for all evaluated characteristics, except for resistance to the leafminer, for which they were equal to the donor parent. Genotypes A3.8, A2.1, and A5.6 were closer to the recurrent parent, with elite breeding line A3.8 being the most similar.