Response of the legume Macrotyloma axillare 'Java' to different inoculum levels of Meloidogyne javanica and defence responses

This study aimed to examine the relationship between Macrotyloma axillare 'Java' and Meloidogyne javanica at different levels of nematode inoculum, and to assess the activity of plant defence enzymes in the presence of nematodes. In Experiment 1, 'Java' and soybean (control) were inoculated with 300 to 8000 eggs + second-stage juveniles (J2) of M. javanica in two different periods (Trials 1 and 2). To confirm the results, a third trial was conducted using 1000 to 4000 eggs + J2 per plant. In Experiment 2, beta-1,3-glucanase (GLU), phenylalanine ammonia-lyase (PAL), peroxidase (POX), and polyphenol oxidase (PPO) activities were measured in non-inoculated plants and in plants inoculated with 2000 eggs + J2. 'Java' presented a reproduction factor (RF) < 1 at all inoculum levels in Trial 1 (RF of 0.17-0.78) and at 2000, 3000, and 6000 eggs + J2 in Trial 2 (RF of 0.47, 0.86, and 0.59, respectively). In Trial 3, 'Java' showed a RF < 1 at all inoculum levels except for 3000 eggs + J2 (RF = 1.1). There was no difference in 'Java' vegetative variables in relation to inoculum levels in any experiment. In Experiment 2, inoculated plants showed increased GLU, PAL, POX, and PPO activities, when compared with non-inoculated plants. 'Java' appears to be moderately resistant to M. javanica, reducing nematode reproduction at different inoculum levels. The plant exhibits increased GLU, PAL, POX, and PPO activities in the presence of M. javanica.