Seleção de fungos visando a produção de um bioherbicida para o controle de Conyza sp.

Abstract

One of the great challenges when working with large-scale agriculture is undoubtedly control the insertion and dissemination of weeds in the growing areas. Most of the weed control is done through chemical control. Although chemical control provides satisfactory results, its unregulated and continuous use can cause many problems such as soil contamination, water bodies, food, and the development of resistant weeds. Conyza sp, in particular, has been causing so many losses in the agricultural areas due to its rapid spread and ease of adaptation to adverse conditions, as well as certain herbicides. From this point, the present work aims at the collection, selection and identification of a microorganism, belonging to the Pampa Biome, aiming the production of secondary metabolites (phytotoxins) that show herbicidal activity in the control of Conyza sp. Within this context, 126 microorganisms were collected and isolated from weeds with disease symptoms, belonging to the pampa biome. For the selection of the microorganism with greater herbicidal activity, pre-emergence and post-emergence and puncture tests were performed in two test plants, Cucumis. sativus and Sorghum bicolor. After the tests, the SO 210 treatment was selected, and the microorganism was responsible for its production, identified as a fungus of the genus Fusarium fujikuroi. From the choice of the microorganism, the standardization of fermentation conditions was performed to improve the efficiency of the treatment. These conditions were defined as being: 10 g / L sucrose, 5% corn steepening water, 220 rpm agitation, pH 7, 25øC temperature and 7-day fermentation time. Once the fermentation conditions were standardized, the SO 210 treatment (fermented broth) was formulated with different concentrations of adjuvants (Assist® mineral oil and Tween 80® and Span® 80 surfactants). The evaluation of the best formulation was carried out by means of a powder-emergency test with Conyza sp. Thus, it was found that the best formulation to be used in the SO 210 treatment consists of the following concentrations; 41.5% fermented broth, 3% Assist® mineral oil and 5.5% Tween 80® and Span® 80 surfactants, resulting in a high EHL, ranging from 9.7 to 15. Finally, it is concluded that the treatment produced by the microorganism Fusarium fujikuroi, under the conditions of submerged fermentation and formulation mentioned above, presents a high potential for post-emergence control of plants of Conyza sp