de Luna Lilian Z, Watson Alan K, Paulitz Timothy C
Graduate Student, Department of Plant Science, McGill University, 21,111 Lakeshore Road, Ste-Anne-de-Bellevue, Québec, Canada H9X 3V9 and Scholar, International Rice Research Institute, DAPO 7777, Metro Manila, Philippines.
Professor, Department of Plant Science, McGill University, and Weed Scientist (Seconded from McGill University), International Rice Research Institute.
Plant Dis. 2002 May;86(5):470-476. doi: 10.1094/PDIS.2002.86.5.470.
Isolates of Curvularia species were collected from weedy Cyperaceae species and are being evaluated as possible biocontrol agents of sedge weeds in rice (Oryza sativa). Curvularia species have been reported from rice; thus cultivars of rice were tested to determine rice seedling responses to these potential biocontrol agents. All 13 rice cultivars were resistant to Curvularia tuberculata isolate 93-022, 12 were resistant to C. tuberculata isolate 93-020, and 7 were resistant to C. oryzae isolate 93-061. In the resistant cultivars, lesions on the leaf laminae were small, light to dark brown, with a dry appearance. Spots on the leaf margins and leaf tips were light brown to cream and dry. In the susceptible cultivars, the brown lesions coalesced with necrotic centers. Sporulation was observed in the lesions on susceptible cultivars but not on the resistant cultivars. The histopathology of C. tuberculata and C. oryzae was studied in two resistant rice cultivars, IR 64 (IRRI Acc. no. 66970) and Norin 21 (IRRI Acc. no. 7686), by light microscopy. C. tuberculata exhibited polar germination beginning at 4 h postinoculation (HPI); whereas C. oryzae was characterized by bipolar germination starting at 2 HPI. Simple terminal or intercalary appressoria were initiated at 24 HPI over stomatal apertures, or rarely, on the epidermal cell walls and bulliform cells. No infection cushions were formed. Penetration occurred by the formation of a fine penetration peg beneath the appressorium. A chlorotic reaction was observed in areas beneath and adjacent to the appressoria and germ tubes and in the infected cells. Resistance of IR 64 and Norin 21 to C. tuberculata and C. oryzae infection was mainly expressed after penetration as a slow and restricted mycelial growth and no sporulation. C. tuberculata isolate 93-022 is the preferred isolate for further study as a biological control agent against Cyperus difformis, C. iria, and Fimbristylis miliacea.
弯孢属物种的分离株采自莎草科杂草，并作为水稻（Oryza sativa）中莎草科杂草可能的生物防治剂进行评估。水稻中已报道过弯孢属物种；因此，对水稻品种进行了测试，以确定水稻幼苗对这些潜在生物防治剂的反应。所有13个水稻品种对弯孢瘤孢菌分离株93 - 022具有抗性，12个对弯孢瘤孢菌分离株93 - 020具有抗性，7个对稻弯孢菌分离株93 - 061具有抗性。在抗性品种中，叶片上的病斑较小，呈浅褐色至深褐色，外观干燥。叶缘和叶尖的斑点为浅褐色至米色，且干燥。在感病品种中，褐色病斑合并形成坏死中心。在感病品种的病斑上观察到了孢子形成，但在抗性品种上未观察到。通过光学显微镜研究了两个抗性水稻品种IR 64（IRRI编号66970）和Norin 21（IRRI编号7686）中弯孢瘤孢菌和稻弯孢菌的组织病理学。弯孢瘤孢菌在接种后4小时（HPI）开始表现出极性萌发；而稻弯孢菌的特征是在接种后2小时开始双极萌发。在24 HPI时，在气孔孔口上方开始形成简单的顶端或居间附着胞，或很少在表皮细胞壁和泡状细胞上形成。未形成侵染垫。通过在附着胞下方形成细的侵入钉进行侵入。在附着胞和芽管下方及相邻区域以及受感染细胞中观察到了褪绿反应。IR 64和Norin 21对弯孢瘤孢菌和稻弯孢菌感染的抗性主要在侵入后表现为菌丝生长缓慢且受限，且不形成孢子。弯孢瘤孢菌分离株93 - 022是作为防治异型莎草、碎米莎草和粟米草的生物防治剂进一步研究的首选分离株。
