Objetivou-se, com esse estudo, isolar e selecionar rizobactérias autóctones de arroz, com potencial para o controle in vitro de Pyricularia grisea, para o controle de fungos veiculados por sementes e para a promoção de crescimento em plântulas de arroz. Para isso, foram isoladas 18 rizobactérias autóctones de arroz, as quais foram submetidas ao teste de antibiose in vitro, em que se avaliou o índice de velocidade de crescimento micelial e o percentual de inibição de crescimento micelial. No tratamento de sementes com rizobactérias, as sementes foram bacterizadas e, posteriormente, avaliou-se a qualidade sanitária (incidência de fungos), a qualidade fisiológica (vigor, germinação e índice de velocidade de germinação de sementes) e a promoção de crescimento das plântulas. No teste de antibiose, todos os isolados apresentaram potencial de antagonismo frente à P. grisea. Houve melhorias na qualidade sanitária das sementes de arroz. Contudo, os isolados não apresentaram efeito positivo sobre a qualidade fisiológica das sementes. Três isolados induziram os maiores incrementos de parte aérea e raiz de plântulas de arroz na promoção de crescimento. Assim, conclui-se que as rizobactérias testadas apresentaram potencial de controle in vitro de fungos, em especial a P. grisea, e também para promoção de crescimento de plântulas de arroz.
ABSTRACT:The aim of this study was to identify the diversity of the parasitic mycoflora and to identify the necessary time until the beginning of the parasitism of sclerotia of Sclerotinia sclerotiorum in soils of the western frontier of the state of Rio Grande do Sul (RS), Brazil. Agricultural and non agricultural soils of five locations in the western frontier of Rio Grande do Sul were collected. The fungi isolation was performed by testing baits, and baits were the sclerotia of the phytopathogen, which remained buried in the soil for 15, 30 and 60 days. The fungi were identified at the genus level. The following fungal genera were found parasitizing sclerotia: Trichoderma, Penicillium, Aspergillus, Fusarium, Pythium (Cromista) Clonostachys rosea (Gliocladium), Chaetomium, Curvularia, Phytophthora (Cromista), Rhizopus, Lichtheimia (Absidia), Mucor, Acremonium, Periconia and Isaria. It was observed that the sclerotia were parasitized by fungi until 15 days after they had been buried. And after this period, only the frequency of occurrence of fungi has changed. It was concluded that the fungal genera Isaria, Periconia, Acremonium, Lichtheimia (Absidia), Phytophthora, Curvularia and Chaetomium are found both in agricultural and non-agricultural soils on the western frontier of RS, but they were not previously cited in other works. There is diversity of parasitic fungi of sclerotia of S. sclerotiorum in the soils of the western frontier of the RS, which can be used in experiments to compose biological control programs for this pathogen. The sclerotia are parasitized by fungi until 15 days after being buried underground. Periconia, Acremonium, Lichtheimia (Absidia), Phytophthora, Curvularia e Chaetomium são encontrados em solos agrícolas e não agrícolas na fronteira oeste do RS, e não foram citados anteriormente em outros trabalhos. Existe diversidade de fungos parasitários de escleródios de S. sclerotiorum nos solos da fronteira oeste do RS, os quais podem ser utilizados em experimentos para compor um programa de controle biológico desse fitopatógeno. Os escleródios são parasitados pelos fungos durante até 15 dias, após os mesmos serem enterrados no solo. KEYWORDSPALAVRAS-CHAVE: estrutura de resistência; mofo branco; controle biológico.
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