Bacillus-Based Products to Control Meloidogyne incognita Races 3 and 4 in Cotton and Compared Histopathology Using B. methylotrophicus

Cotton meloidoginosis caused by Meloidogyne incognita races 3 and 4 is an important disease and can cause intense damage. The objective of this work was to test the effectiveness of commercial Bacillus-based products in the control of M. incognita races 3 and 4 of cotton in a greenhouse. Plants with and without nematode inoculation were used and subsequently evaluated for 200 days after the application of treatments. The products with Bacillus subtilis, B. amyloliquefasciens and B. subtilis + B. lincheniformis showed the best results in terms of shoot fresh matter weight. In relation to shoot dry weight, treatments with B. methylotrophicus (87 g, with nematode) and B. subtilis (80 g, with nematode) were superior, with emphasis on B. methylotrophicus. In the evaluation of root fresh weight, only the treatment with B. methylotrophicus (148.8 g, with nematode) provided statistically higher weight than the control. In item dry weight of root without nematode and nematode reproduction factor, the treatment with B. methylotrophicus stood out from the other treatments, making this the selected product to conduct the subsequent tests. With the acid fuchsin staining method, it was possible to verify that there was reduction in the penetration of J2 in the first days for plants treated with the bacteria. Upon adoption of the toluidine blue staining method, it was possible to observe abnormalities in giant cells with formation of vacuoles, thinner cell wall and females with large vacuoles inside. Thus, there is evidence that the use of biological products can be effective in controlling M. incognita.