Estimativa de parâmetros genéticos para características de resistência ao Meloidogyne incognita em alface

Abstract

The use of resistant cultivars is the ideal method for the control of root-knot nematode on lettuce. Knowing genetic aspects related to resistance to the pathogen becomes important for decision making and the establishment of improvement strategies. Therefore, the objective of the research was to estimate and analyze genetic and phenotypic parameters for the resistance reaction of lettuce to the root-knot nematode Meloidogyne incognita. The cultivars Salinas 88 (resistant) and Regina 71 (susceptible) were used as parents to cross and obtain the F1 and F2 populations to be evaluated, together with the parents, for resistance to M. incognita. The characteristics evaluated were: number of total eggs per plant (NE), number of eggs per gram of root (NEGR), reproduction index (RI), reproduction index per gram of root (RIGR) and reproduction factor (RF). The estimated parameters were: phenotypic and genotypic variances, broad-sense heritability, average degree of dominance, measure of additive and dominance effects, and gains by selection. Populations were also classified for resistance reaction based on percentage reduction in reproduction factor (RRF). It was possible to observe relatively high broad-sense heritability, presence of additive effects of alleles and occurrence of transgressive segregation, especially for NE and RIGR traits, which indicates the possibility of gains in selection. Cultivar 'Regina 71' was classified as highly susceptible, 'Salinas 88' as moderately resistant and F1 and F2 generations as susceptible. Finally, it was concluded that there is genetic variability for resistance to M. incognita, from the crossing between the cultivars Regina 71 and Salinas 88 and that the cultivar Salinas 88 proved to be a viable source of resistance to M. incognita to be used in breeding programs.