Six pathogenic fungal species were isolated from naturally-infected Echinochloa species and evaluated as biological control agents for E. crus-galli, E. colona, and E. glabrescens in rice. Bipolaris sacchari, Curvularia geniculata, and Exserohilum monoceras were non-pathogenic to rice and caused high mortality of Echinochloa species. E. monoceras was selected for further study. Under regulated greenhouse conditions, an inoculum dose of 2.5 $ times$ 10$ sp7$ conidia/m$ sp2$ killed E. crus-galli and E. glabrescens seedlings while 5.0 $ times$ 10$ sp7$ conidia/m$ sp2$ caused 100% mortality of E. colona seedlings. The 1.5-leaf stage was the most susceptible growth stage for all three Echinochloa species. E. glabrescens was most susceptible to E. monoceras infection, E. crus-galli had an intermediate susceptibility, and E. colona was least susceptible. The optimum temperature for 100% mortality was between 20 and 30 C for all Echinochloa species, whereas the minimum dew period for 100% mortality was 16 h for E. colona, 12 h for E. crus-galli, and 8 h for E. glabrescens. Under screenhouse conditions and in the absence of an artificial dew period, over 90% of Echinochloa seedlings were killed when inoculum was sprayed in an oil emulsion or when applied as a dry powder to the water surface of a simulated paddy field. Maximum conidia production occurred on V-8 juice agar or centrifuged V-8 juice agar, at 28 C in the dark. No conidia were produced in liquid media. Of various agricultural products tested as solid substrates, the highest sporulation (1.81 $ times$ 10$ sp6$ conidia/g dry weight) occurred on corn leaves. Host range tests on 54 plant species in 43 genera and 19 families showed that Rottboellia cochinchinensis, was also highly susceptible to this fungus. Of the crops tested, only corn seedlings were lightly infected under optimum greenhouse conditions but no disease occurred on corn under field conditions. Bipolaris sacchari, Exserohilum monoceras, and E. oryzae
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.40293 |
| Date | January 1996 |
| Creators | Zhang, Wenming |
| Contributors | Watson, A. K. (advisor) |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Plant Science.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001505818, proquestno: NN12517, Theses scanned by UMI/ProQuest. |
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