Hongos asociados a la pudrición del cacao theobroma cacao l. en el soconusco, Chiapas y patogenicidad y control in vitro de nodulosporium.

"The cocoa crop Theobroma cacao L. is an agroecosystem highly favorable for the development of diseases. The most important and greatest impacting problems worldwide are the phytopathogenic fungi, mainly three species; Moniliophthora roreri, Moniliophthora perniciosa and Phytophthora palmivora with losses of 80-100% in production. Fruit rot is an important infection factor in cocoa, due to dissemination agents such as air and fruit infection at any time, susceptible tissue presence and favorable environmental conditions. The present work was carried out because research on fruit rot for Soconusco region, Chiapas is scarce and the lack of adequate management to reduce damage caused by this disease. The incidence and severity of cocoa rot in infected fruits in cocoa trees was evaluated in two plots in 2014 and 2015. The severity was evaluated by the external symptomatic scale for moniliasis rotting and the incidence was calculated as the number of fruits that showed disease symptoms (%). The morphological identification of fungi associated with cocoa fruit was carried out and the genus Nodulosporium was highlighted, which was also identified morphometrically and molecularly using universal primers ITS4 and ITS5. With this genus, pathogenicity tests were carried out on foliage and fruit at 1x108 spores/mL concentration. In vitro biological control tests were carried out, Nodulosporium with Trichoderma harzianum and Bacillus subtilis and chemical control products: azoxystrobin, chlorothalonil and thiabendazole. The parameters were examined with analysis of variance and comparison of Tukey means (P <0.05), using SAS software. The percentage of affected fruits and the degree disease severity was greater during 2014 in both production plots, compared to 2015, with significant differences between these years; this difference was influenced by precipitation, which was greater during the first year, and between both locations during the same year there was no significant difference, which indicates that height does not influence the disease incidence and severity. Various spore fungi were isolated from fruit damaged tissue and diseased plant tissue; Aspergillus sp., Colletotrichum sp., Fusarium sp., Lasiodiplodia theobromae, Nodulosporium sp., Penicillium sp., Rhizopus sp., Trichoderma sp., Verticillium sp., and two unrecognized fungi were found. The absence of important phytopathogenic fungi in cocoa agroecosystem is highlighted. In this study, the presence of Nodulosporium fungus in cocoa fruits was recorded for Chiapas, México and its teleomorph is identified as Hypoxylon; the two latter also corroborated morphometrically and molecularly. In pathogenicity tests with cocoa foliage crop, it was found that Nodulosporium is slightly pathogenic, causing chlorosis and dehydration of the leaf. The biological control of phytopathogen Nodulosporium with the antagonist B. subtilis and T. harzianum in confrontation exert a significant inhibitory effect on the phytopathogen with 71.86 and 69.93% respectively; even T. harzianum overcame the pathogen, placing it in class 1 of Bell antagonism. Nodulosporium sp., Showed susceptibility to the action of fungicides azoxystrobin, chlorothalonil and thiabendazole added in PDA medium. Thiabendazole was more effective; with 2.5 ppm inhibited mycelial growth of the fungus, followed by chlorothalonil that at 1000 ppm no longer allows the fungus growth and azoxystrobin, although, less effective, since it requires high concentrations above 1000 ppm to have a good control. Recognize the pathogens diversity associated with cocoa crop, its incidence, severity and pathogenicity is utmost importance, because they can pose a threat to the crop in the future. The chemicals products azoxystrobin, chlorothalonil and thiabendazole and the biological control agents T. harzianum and B. subtilis are efficient for in vitro control of Nodulosporium sp. fungus."