Reaction of soybean cultivars to the root-knot nematode Meloidogyne javanica
Meloidogyne javanica is one of the main nematodes that attack soybean crops and although genetic resistance is the ideal control measure, few cultivars are described as resistant among the innumerous cultivars recommended for the Central Region of Brazil. In this context, we aimed to evaluate the reaction of 29 soybean cultivars to M. javanica. Two experiments were conducted under greenhouse conditions in a completely randomized design with six replications. The plants were inoculated with a suspension of 2000 eggs and J2 of M. javanica and the evaluations occurred sixty days after the inoculation (DAI), determining the nematode population density and the reproduction factor. Based on the results from these two experiments we conducted another experiment selecting four soybean cultivars, one moderately resistant and three with an unknown behavior. These cultivars were inoculated with different concentrations of M. javanica inoculum. The experiment was conducted in a completely randomized design in a 4 x 4 factorial scheme with twelve replications. Evaluations were carried out at 10 DAI by observing the number of J2 and J3/ root system. At 45 DAI the nematode population density in the roots was evaluated. Of the soybean cultivars tested, none behaved as resistant. However, the cultivars UFU Carajás and BRSGO Paraíso presented less M. javanica development in the roots compared to the P98Y70 and NS 7478 and as the inoculum pressure was increased, the penetration and development of the nematode in the roots increased.
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