Controle genÃtico da resistÃncia à Meloidogyne incognita nas cultivares de alface Grand Rapids e Salinas 88 / Resistance of the lettuce cultivar Salinas 88 to Meloidogyne incognita (Kofoid &White) Chitwood.

AUTOR(ES)
DATA DE PUBLICAÇÃO

2006

RESUMO

In spite of the advances in plant breeding, horticulture still faces problems such as the incidence of root-knot nematodes (Meloidogyne spp.), which are difficult to control. Varietal resistance is the most efficient and economical form of controling the pathogen. Few studies have been effected on nematode resistance in lettuce and its genetic control. These studies have reported the presence of resistance genes in some looseleaf and crisphead lettuce cultivars, which are nonetheless poorly adapted to growth under Brazilian conditions. There are no reports on nematode resistance in butterleaf lettuce types. The crisphead lettuce cultivar Salinas 88 is resistant to the root-knot nematodes, but the genetic control of this resistance has not yet been studied. This work was intended to study the inheritance of resistance to the root-knot nematode Meloidogyne incognita conferred by the cultivar Salinas 88, and to identify lettuce lines homozygous for resistance to the trait, as a step towards ultimately obtaining nematode resistant butterleaf types. In addition to the parental cultivars Salinas 88 (resistant, crisphead lettuce) and Regina 71 (susceptible, butterleaf lettuce), the F1 and F2 generations were used in the study, in addition to F4 families selected from the segregating F2 population. Plants grown for 45 days in substrate infected with eggs of Meloidogyne incognita race 1 were examined for gall incidence, gall number scores and eggmass number scores. Generation mean components and associated genetic parameters were estimated through the weighted least squares procedure. Hypotheses of monogenic inheritance were tested for different presumed degrees of dominance, and the maximum likelyhood procedure was used to test the presence of a major gene, associated or not with minor polygenic effects. There was evidence of the presence of a major gene, with nematode resistance being under control of a partially dominant allele, whose action was nevertheless influenced by minor polygenic effects. The high frequency (>50%) of homozygous nematode resistant F4 families was consistent with these findings

ASSUNTO(S)

melhoramento vegetal

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