Response of Soybean Cultivars to Oxidative Stress caused by Meloidogyne javanica.

The present study aimed to investigate the response of soybean cultivars with different susceptibility levels to the root-knot nematode Meloidogyne javanica at varied time intervals by analyzing the initial plant-nematode interaction using antioxidant enzymes as oxidative stress markers. A 4 × 4 × 2 factorial method with 5 repetitions was used to analyze 4 soybean cultivars at 4 different collection times-6, 12, 24, and 48 h-with and without M. javanica inoculation. The parameters evaluated were the activities of antioxidant enzymes phenol peroxidase (POX) and ascorbate peroxidase (APX); the concentrations of hydrogen peroxide (H2O2) and malondialdehyde (MDA); and the number of M. javanica juveniles penetrated into each plant. H2O2 concentration varied among the cultivars with and without inoculation and at different collection times as indicated by MDA concentration and POX and APX activities, demonstrating a rapid response of the host to an infection by M. javanica. Oxidative stress caused by M. javanica did not vary among the soybean cultivars regardless of their susceptibility level; however, the antioxidant enzymes POX and APX responded according to the susceptibility level of the cultivars.

Reproduction of Meloidogyne javanica in soybean genotypes.

Meloidogyne javanica is among the most important nematodes that damage soybean, and although genetic resistance is the ideal control measure, there are few cultivars described as resistant among those recommended for southern Brazil. The objective of this work was to evaluate the reaction of soybean cultivars to M. javanica. The inoculum of nematodes (Est. J3) was obtained from soybean plants and inoculated into tomato plants cultivar "Santa Cruz". Thirty-seven soybean cultivars widely used in the South, Southeast and Midwest of Brazil were used in the experiment. For each plant a suspension of 5,000 eggs + juveniles of second stage of M. javanica was inoculated into a sterile soil hole in 2-liter pots with six replications. The evaluation of root weight, number of galls, number of nematodes was 60 days after M. javanica inoculation. The results were subjected to analysis of variance, and the averages of each treatment were compared to each other by the Scott-Knott cluster test at 5% probability. Even though M. javanica presented RF> 1.00 in all soybean genotypes tested, different levels of susceptibility were observed. Thus, the lowest reproduction of the root-knot nematode was observed in M ​​5947 IPRO, HO AMAMBAY IPRO, BMX GARRA IPRO and FPS ATALANTA.