Phytosanitary quality of Brachiaria brizantha 'BRS Piata seeds in function of climate conditions/Qualidade sanitaria de sementes de Brachiaria brizantha 'BRS Piata' em funcao de condicoes climaticas

Infected seeds are one of the main pathogen transmission vehicles, and they are responsible for significant losses in production fields; phytosanitary defense depends on the inoculum and climatic factors. Thus, in this study, it was aimed to identify climatic variables of the regions that propitiate the production of Brachiaria brizantha 'BRS Piata' seeds infected with phytopathogenic fungi. Temperature and rainfall data were obtained from 10 production fields, and phytosanitary quality of the seeds was evaluated with the filter paper method; the means were compared using the Kruskal-Wallis non-parametric analysis. Principal component analysis was performed to determine the relationship between the climatic variables and seed phytosanitary quality. Sites with maximum temperatures higher than 30[degrees]C, mean values close to 25[degrees]C, and rainfall less than 82 mm during harvest were favorable to the incidence of Fusarium spp. The incidence of Bipolaris sp. in the seeds of Piata grass was favored by temperatures around 19 and 20[degrees]C during the maturation phase. The highest incidence of Exserohilum sp. occurred at the sites in which the temperature during harvest was close to 20[degrees]C and accumulated rainfall, between 167 and 181 mm. Key words: forage grasses, Piata grass, temperature, humidity, phytosanitary barrier A semente infectada e um dos principais veiculos de transmissao de patogenos, responsaveis por perdas significativas em campos de producao e, as condicoes sanitarias destas dependem do inoculo e dos fatores climaticos presentes. Assim, objetivou-se identificar variaveis climaticas das regioes que propiciam a producao de sementes de Brachiaria brizantha, cv. BRS 'Piata', infectadas com fungos fitopatogenicos. Foram obtidos dados de temperatura e precipitacao de 10 campos de producao e a sanidade das sementes foi avaliada pelo metodo do papel de filtro, com as medias comparadas pela analise nao-parametrica de Kruskal-Wallis. Para determinar a relacao entre variaveis climaticas e a sanidade das sementes aplicou-se a analise de componentes principais. Locais com temperaturas maximas superiores a 30[degrees]C, medias proximas a 25[degrees]C e acumulo de chuva inferior a 82 mm na colheita foram favoraveis a incidencia de Fusarium spp.. A incidencia de Bipolaris sp. em sementes de capim-piata na fase de maturacao e favorecida por temperaturas em torno de 19 e 20[degrees]C. A maior incidencia de Exserohilum sp. ocorre em locais cuja tempe