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一叶瘟病斑分离得到的稻梨孢菌（Pyricularia oryzae）菌株的毒力。选取处于四叶期的小麦品种（BRS Louro、BR 18、BRS Tarumã、BRS Parrudo、BRS 208），以浓度为100000个分生孢子/mL的悬浮液进行接种。研究观察到不同小麦品种的病害严重度存在显著差异；在所评估的菌株中，各品种的感病性亦存在差异。各处理的病害严重度介于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。其中，BRS 208与菌株1互作的病害严重度最高（99.54%），其次为BRS Louro与菌株2（99.34%）以及BRS 208与菌株2（99.09%）。最低病害严重度分别出现在菌株1接种的BRS Tarumã品种（68%），以及菌株2接种的BR 18品种（75%）。菌株3的致病力处于中等水平，各供试品种的病害严重度介于44%至58%之间。菌株4对所有供试品种的致病力最弱，其病害严重度指数介于3%至12%之间。上述数据表明，从单一病斑分离得到的稻梨孢菌（Pyricularia oryzae）菌株存在毒力多样性。