Diversity of virulence of Pyricularia oryzae isolates obtained from a single lesion of wheat

ABSTRACT The objective of this study was to evaluate the virulence of Pyricularia oryzae isolates obtained from a single leaf blast lesion on wheat. The wheat cultivars (BRS Louro, BR 18, BRS Tarumã, BRS Parrudo, BRS 208) at the four-leaf stage were inoculated with a suspension of 100.000 conidia/mL. A significant difference was observed in the severity in the cultivars. Among the evaluated isolates, it was possible to observe differences in the susceptibility of the cultivars. Severity data ranged from 3.3 to 99.54% among treatments. Isolates 1 and 2 were the most aggressive for all cultivars tested. The greatest disease severity occurred in the interactions BRS 208 x isolate 1 (99.54%), BRS Louro x isolate 2 (99.34%), and BRS 208 x isolate 2 (99.09%).The lowest disease severity was observed in BRS Tarumã (68%) and BR 18 (75%) cultivars for the isolates 1 and 2, respectively. Isolate 3 presented medium aggressiveness in which the cultivars presented between 44 to 58% of wheat blast severity. The isolate 4 was the least aggressive for all cultivars with severity indexes ranging from 3 to 12%. These data indicate the existence of virulence diversity in P. oryzae isolates obtained from a single lesion.

摘要 本研究旨在评估从小麦单叶瘟病病斑分离得到的稻梨孢菌（Pyricularia oryzae）菌株的毒力。供试小麦品种包括BRS Louro、BR 18、BRS Tarumã、BRS Parrudo、BRS 208，于四叶期用浓度为100000个分生孢子/mL的悬浮液接种。各品种的病情严重度存在显著差异。在所评估的菌株中，不同品种的感病性亦存在差异。各处理的病情严重度介于3.3%至99.54%之间。菌株1与菌株2对所有供试品种均表现出最强的致病力。病情严重度最高的互作组合为BRS 208 × 菌株1（99.54%）、BRS Louro × 菌株2（99.34%）以及BRS 208 × 菌株2（99.09%）。病情严重度最低的组合分别为BRS Tarumã接种菌株1（68%）、BR 18接种菌株2（75%）。菌株3的致病力处于中等水平，各供试品种的小麦瘟病病情严重度介于44%至58%之间。菌株4对所有供试品种的致病力最弱，其病情严重度指数介于3%至12%之间。上述数据表明，从单个病斑分离得到的稻梨孢菌菌株存在毒力多样性。