Micro-organismos, quitina e quitosana no manejo de nematoides das galhas no tomateiro

Abstract

Among the forms of plant-parasitic nematode management, biological control with soil microorganisms and the induction of resistance stand out. This study evaluated the effectiveness of microorganisms, chitin and chitosan in the management of root-knot nematodes on tomato. Three experiments were done to confirm such effectiveness. The first experiment evaluated the effectiveness of the commercial product LMXBIO and each microorganism of its composition (B. subtilis, B. thuringiensis, Rhizobium sp., S. cerevisiae and Trichoderma spp.) alone, to control M. incognita and M. javanica and their effects on tomato plant growth. The second experiment evaluated the sensitivity of the above microorganisms to agrochemicals imidacloprid, benalaxyl + mancozeb, kasugamycin and metribuzim. The third experiment evaluated the effectiveness of HYT-C products (chitin) and/or HYT-D (chitosan), via soil and/or leaf, to control M. incognita and M. javanica and their effect on tomato plant growth. Trichoderma spp. was effective in reducing M. incognita in tomato, while B. subtilis and Rhizobium sp. were effective in reducing M. javanica in tomato. At the recommended concentrations for tomato, the fungicide benalaxyl + mancozeb inhibited growth of B. thuringiensis and Rhizobium sp.; the herbicide metribuzin inhibited growth of B. thuringiensis and reduced the rate of mycelial growth Trichoderma sp.; the bactericide kasugamycin inhibited growth of B. thuringiensis. At the recommended concentrations for tomato crop, no products inhibited growth of B. subtilis or S. cerevisiae. The insecticide imidacloprid did not affect the development of any of the studied microorganisms. Chitin in the soil increased root length and t fresh weight in plants inoculated with M. incognita. When combined with foliar chitosan, it also promoted increased plant shoot mass. The application of chitin to soil associated with chitosan to leaves, reduced the reproduction factor and population per gram of the root-knot nematode M. javanica. No significant results were obtained for M. incognita. Chitin applied to the soil increased the population of chitinolytic microorganisms. The application of soil chitin, foliar chitosan and the combination of both, increased the activity of the enzyme chitinase in the leaves four days after application, regardless of the nematode inoculated.