Abstract
ABSTRACT Genetic resistance is the most suitable mechanism to control root-knot nematodes in lettuce. However, information about the resistance levels of currently used lettuce cultivars is scarce in the literature. Thus, the objective of this research was to characterize lettuce cultivars for resistance to root-knot nematodes Meloidogyne incognita (Mi) and M. javanica (Mj), aiming the identification of resistance sources for breeding, and to transfer information to the productive sector. We evaluated 97 lettuce genotypes in tree trials. In the first one (preliminary assessment), 92 lettuce genotypes were inoculated simultaneously with M. incognita race 1 and M. javanica species, 17 days after sowing. The gall index (GI) was evaluated 41 days after inoculation. In the second trial nine genotypes, selected from the first trial, were evaluated; and in the third trial, two new cultivars from Embrapa were evaluated. In the last two trials, the nematode species were inoculated separately, and the egg mass index (EMI), number of eggs per gram of roots (NEGR) and reproduction factor (RF) were also evaluated. In both trials, the lettuce cultivars Salinas 88 and Grand Rapids were used as resistant controls, as well as cultivar Irene as the susceptible control. The data were submitted to analysis of variance and treatments means grouping by Scott-Knott´s test. The crisp leaf cultivars presented a higher degree of resistance to the root-knot nematodes compared to the smooth leaf type cultivars. Cultivars Vera and Amanda present resistance to M. incognita, and Vanda to M. javanica. ‘Salinas 88’ present resistance mainly to M. javanica; while cultivar Mônica and the Embrapa cultivars BRS Leila and BRS Mediterrânea are resistant to both nematode species.
Highlights
A resistência genética é o mecanismo mais indicado para o controle dos nematoides-das-galhas em alface
Salinas 88 apresenta resistência principalmente a M. javanica; enquanto a cultivar Mônica e as cultivares da Embrapa BRS Leila e BRS Mediterrânea, são resistentes a ambas as espécies de nematoides
Due to intensive cultivation of this vegetable, and because most lettuce cultivars are highly susceptible to root-knot nematodes (Campos et al, 2001; Pinheiro, 2017), the nematode populations have increased in production areas, causing considerable economic damages (Rabello, 2010; Pinheiro, 2017)
Summary
A resistência genética é o mecanismo mais indicado para o controle dos nematoides-das-galhas em alface. Dessa forma, o objetivo do trabalho foi caracterizar genótipos de alface quanto à resistência aos nematoides-das-galhas, Meloidogyne incognita (Mi) e M. javanica (Mj), visando a identificação de fontes de resistência para utilização no melhoramento, e o repasse de informações para o setor produtivo. Somados aos genótipos avaliados em cada ensaio, foram utilizadas como testemunhas resistentes as cultivares de alface Salinas 88 e Grand Rapids, e como suscetível a cultivar Irene. The objective of this research was to characterize lettuce cultivars for resistance to root-knot nematodes Meloidogyne incognita (Mi) and M. javanica (Mj), aiming at the identification of resistance sources for breeding, and the transfer of information to the productive sector
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