Departamento de Fitossanidade, Universidade Federal do Rio Grande do Sul, 91540-000, Porto Alegre, RS, Brazil.
Departamento de Fitopatologia, Universidade Federal de Viçosa, 36570-000, Viçosa, MG, Brazil.
Plant Dis. 2018 Jul;102(7):1341-1347. doi: 10.1094/PDIS-12-17-1943-RE. Epub 2018 Apr 30.
Fusarium graminearum of the 15-acetyl-deoxynivalenol (15-ADON) chemotype is the main cause of Fusarium head blight (FHB) of wheat in southern Brazil. However, 3-ADON and nivalenol (NIV) chemotypes have been found in other members of the species complex causing FHB in wheat. To improve our understanding of the pathogen biology and ecology, we assessed a range of fitness-related traits in a sample of 30 strains representatives of 15-ADON (F. graminearum), 3-ADON (F. cortaderiae and F. austroamericanum), and NIV (F. meridionale and F. cortaderiae). These included perithecia formation on three cereal-based substrates, mycelial growth at two suboptimal temperatures, sporulation and germination, pathogenicity toward a susceptible and a moderately resistant cultivar, and sensitivity to tebuconazole. The most important trait favoring F. graminearum was a two times higher sexual fertility (>40% perithecial production index [PPI]) than the other species (<30% PPI); PPI varied among substrates (maize > rice > wheat). In addition, sensitivity to tebuconazole appeared lower in F. graminearum, which had the only strain with effective fungicide concentration to reduce 50% of mycelial growth >1 ppm. In the pathogenicity assays, the deoxynivalenol producers were generally more aggressive (1.5 to 2× higher final severity) toward the two cultivars, with 3-ADON or 15-ADON leading to higher area under the severity curve than the NIV strains in the susceptible and moderately resistant cultivars, respectively. There was significant variation among strains of the same species with regards asexual fertility (mycelial growth, macroconidia production, and germination), which suggested a strain- rather than a species-specific difference. These results contribute new knowledge to improve our understanding of the pathogen-related traits that may explain the dominance of certain members of the species complex in specific wheat agroecosystems.
镰刀菌禾谷种的 15-乙酰脱氧雪腐镰刀菌烯醇（15-ADON）化学型是导致南里奥格兰德州小麦赤霉病（FHB）的主要原因。然而，其他种复合体成员也发现了 3-ADON 和雪腐镰刀菌烯醇（NIV）化学型，它们也会导致小麦赤霉病。为了增进我们对病原菌生物学和生态学的了解，我们评估了 30 株代表菌株的一系列与适应性相关的特性，这些菌株分别属于 15-ADON（禾谷镰刀菌）、3-ADON（尖孢镰刀菌和美洲镰孢）和 NIV（拟分枝镰刀菌和尖孢镰刀菌）化学型。这些特性包括在三种基于谷物的基质上形成子囊壳、在两种亚最佳温度下生长的菌丝体、产孢和萌发、对易感和中度抗性品种的致病性以及对戊唑醇的敏感性。最有利于禾谷镰刀菌的重要特性是其有性生殖力高出其他种两倍（>40%的子囊壳产生指数[PPI]）；PPI 因基质而异（玉米>水稻>小麦）。此外，禾谷镰刀菌对戊唑醇的敏感性似乎较低，其唯一的菌株有效杀菌剂浓度可降低 50%的菌丝体生长>1ppm。在致病性试验中，脱氧雪腐镰刀菌烯醇的产生者通常对两个品种更具侵略性（最终严重度增加 1.5 至 2 倍），在易感和中度抗性品种中，3-ADON 或 15-ADON 导致的严重度曲线下面积分别高于 NIV 菌株。同一物种的菌株之间在无性生殖力（菌丝体生长、大型分生孢子产生和萌发）方面存在显著差异，这表明是菌株而不是种特异性差异。这些结果为提高我们对可能导致特定种复合体成员在特定小麦农业生态系统中占主导地位的病原菌相关特性的理解提供了新的知识。
