Phytosanitary quality of Brachiaria brizantha ‘BRS Piatã’ seeds in function of climate conditions

ABSTRACT 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 Piatã’ 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 °C, mean values close to 25 °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 Piatã grass was favored by temperatures around 19 and 20 °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 °C and accumulated rainfall, between 167 and 181 mm.

摘要 受感染种子是病原菌传播的主要途径之一，可给大田生产造成严重经济损失；植物检疫防控效果取决于病原菌接种体与气候因素。本研究旨在明确可诱导臂形草（Brachiaria brizantha）‘BRS Piatã’产出携带植物病原真菌种子的区域气候变量。研究从10个生产大田获取气温与降雨量数据，采用滤纸法评估种子的植物检疫品质，通过Kruskal-Wallis非参数检验对各组均值进行比较，并运用主成分分析明确气候变量与种子植物检疫品质之间的关联。结果表明：收获期最高气温高于30℃、平均气温接近25℃且降雨量低于82mm的区域，有利于镰孢菌（Fusarium spp.）的侵染发生；皮阿塔草种子中的离蠕孢（Bipolaris sp.）侵染发生率，在成熟阶段气温处于19~20℃左右时显著升高；平脐蠕孢（Exserohilum sp.）侵染发生率最高的区域，其收获期气温接近20℃且累积降雨量介于167~181mm之间。