Caracterização de fungos cercosporóides no Estado do Rio de Janeiro e inibição de crescimento micelial in vitro de Fusarium solani f. sp. piperis (= Fusarium solani) com bactérias promotoras de crescimento vegetal

Abstract

Within the Kingdom Fungi (true fungi) are the imperfect (or asexual phase) fungi of various members of the Ascomycota and some Basidiomycota divisions, known as anamorphic fungi [before Hyphomycetes (including Agonomycetes) and Coelomycetes]. In this group are several genera of fungi that cause diseases that affect the sanity of plants, weeds or of economic importance. Among them are cercosporoid fungi, hyphomycetes responsible for leaf spots and leaf fall (Cercosporioses), and fungi of the genus Fusarium responsible for the fusariosis, which are characterized by the clogging of xylem, wilting, foliar drying, and plant death. This study aimed to characterize species and new taxa of cercosporoid fungi associated with foliar lesions in weeds and cultivated plants of agronomic importance in the State of Rio de Janeiro; and to obtain bacterial strains with antagonistic activity against to Fusarium solani, causal agent of Pepper Fusarium. Symptomatic samples obtained in the areas of the municipality of Seropédica, including the campus of UFRRJ, were taken to the Micology / Phytopathology laboratories of the Department of Entomology and Phytopathology / ICBS and analyzed through an optical and stereoscopic microscopes; isolations were carried out in BDA culture medium for incorporation into the collection of phytopathogenic fungi, and subsequent extraction of genomic DNA from fungal isolates, PCR amplification and sequencing. A total of 20 cercosporoids were studied, in the genera: Camptomeris, Cercospora, Cylindrosporium, Passalora and Pseudocercospora; and15 isolates were molecularly analyzed using the Blast / NCBI analysis present in the Genbank database, and the sequences obtained were analyzed and compared with the use of the MEGA 6 program and generated a "Neighbor-joining" phylogenetic tree (NJ) with 1000 replications. The isolate of Fusarium solani came from producing areas of the municipality of Água Doce do Norte / ES, causing wilt and drying of leaves in pepper plants of 3-4 months of age. The fungus was isolated and its DNA extracted. The bacterial strains were obtained from the EMBRAPA Agrobiology cultures collection located in the municipality of Seropédica, and 29 strains were used, among them Bacillus, Burkholderia, Pseudomonas, Microvirga and Serratia. Double culture was performed on petri dishes containing BDA at ± 28 ° C / 15 days, and an 8 mm mycelial disc was deposited in the center of the plate and the surrounding bacterial strains, totaling 8 plates in the first screening evaluated by the size of the halo of inhibition of mycelial growth formed by bacteria. From these 29 strains, 21were selected, which were again crossed by the double culture procedure for 4 consecutive repetitions, obtaining a total of 5 bacterial isolates [Bacillus (BR 10788), Pseudomonas (BR 10376; BR 10449; BR 10218) and Burkholderia (BR 10920)] with potential for fungus control Fusarium solasni.