Meloidogyne incognita resistant strains of leaf lettuce

The root-knot nematode is a major problem for commercial lettuce cultivation because it affects the market quality of the final product. The objective of this study was to select strains of butter-leaf lettuce resistant to Meloidogyne incognita spp. with good agronomic performance for further cultivar trials. Three field experiments were conducted on the premises of Instituto Agronomico de Pernambuco (IPA-PE) and the Federal Rural University of Pernambuco. The experiments were held from October to November, 2012 and March to April, 2013, respectively. In experiment 1, 14 genotypes were evaluated. In experiment 2, 13 genotypes were evaluated. In Experiment 3, 24 progenies were evaluated. In Experiments 1 and 2, commercial characteristics were evaluated. In experiment 3, resistance to M. incognita spp. was evaluated using the following characteristics: Gall index, number of galls and egg number. All of the tested progeny were considered commercial; when comparing the average number of root galls and number of eggs in the root system, 16 and 22 progenies, respectively, were considered resistant. Among all progeny, 13 were shown to satisfy the commercial standard and have significant resistance to M. incognita. Genotypes were selected that had resistance to M. icognita spp. and high commercial potential for further cultivar trials.   Key words: Lactuca sativa L., plant breeding, strain selection, root-knot nematodes.