Controle biológico do nematoide das galhas em arroz

Abstract

Rice is one of the most consumed cereals in the world, standing out as a staple food of the world population and gall-causing nematodes can damage this crop, with estimates of 80% in yield loss. Much is currently being studied about the action of bacteria acting as biological nematode control agents of galls, which make them an alternative control of this nematode in rice fields. It also minimizes the problem of no rice cultivars resistant to this pathogen. Thus, this study aimed to evaluate the effectiveness of three microbiological nematicides in controlling the nematode of galls Meloidogyne sp.2 and sp.3 in the rice crop. The experiment was conducted under greenhouse conditions at the Federal University of Pampa-UNIPAMPA / Campus Itaqui. The inoculum was obtained by extracting nematode eggs from roots of rice plants kept in pots with nematode infested soil in a greenhouse. The experimental design was completely randomized with five treatments and six replications. The experiment was repeated twice. Three microbiological nematicides (Bacillus subtilis + Bacillus licheniformis, Bacillus amyloliquefaciens isolated BV03 and Bacillus methylotrophicus), one chemical nematicide (Fluensulfone) and one control without application were used. Rice sowing cultivar IRGA 424 was carried out in 500 mL plastic cups filled with autoclaved soil and kept in a greenhouse. The inoculation was carried out with approximately 5000 eggs of Meloidogyne spp. Evaluations were performed at 30 days after inoculation of the first rice experiment; and at 45 days after inoculation of the second experiment. For the evaluation, we counted gall number, number of eggs per root system and fresh root matter. The obtained data were submitted to the analysis of variance and the averages of each treatment, grouped by the Scott-Knott test, at the 5% probability level. According to the results obtained, there was no statistical difference between the filters applied to control root knot nematodes in rice for a variable weight of plant root system, in either of the two evaluated experiments. Regarding the variables, number of galls and eggs per gram of root in the first experiment, although there was no difference in the number of galls per gram of root. In the second experiment, treatment with Bacillus subtilis + Bacillus licheniformis was more effective in reducing galls per root gram, using 68.18% or number of galls per root gram. However, this treatment did not differ from the others in the evaluation of Experiment 1. Results with greater control in Experiment 1 for eggs per gram of root were submitted to tests with Bacillus subtilis + Bacillus licheniformis, Bacillus amyloliquefaciens isolates BV03 and Fluensulfone, which was published from 38 , 69%, 57.47% and 65.13%, respectively, of eggs per gram of roots. In experiment 2, the most effective treatment was with Bacillus amyloliquefaciens isolated BV03, which reduced 77.78% in the number of eggs per gram of root. Based on this, we conclude that the microbiological nematodes Bacillus subtilis + Bacillus licheniformis and Bacillus amyloliquefaciens isolated BV03 try to reduce the number of galls and eggs per gram of root in rice.