Submitted to: Journal of Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/7/2005
Publication Date: 7/20/2005
Citation: Dugan, F.M., Lupien, S.L., Hernandez-Bello, M., Peever, T.L., Chen, W. 2005. Fungi resident in chickpea debris and their suppression of growth and reproduction of didymella rabiei under laboratory conditions. Journal of Phytopathology.153:431-439. Interpretive Summary: Ascochyta blight of chickpea has been a persistent and troublesome disease in eastern Washington and western Idaho, and other chickpea growing areas of the world. The pathogen (Didymella rabiei) is a fungus that can survive the winter in residues left from harvest and spread to new crops the following spring. It has traditionally been controlled by deep plowing, which buried harvest residues, but this practice is now less favored because it promotes soil erosion. The pathogen is capable of long range spread via the sexual stage spores (ascospores) and short range spread by the nonsexual stage spores (conidia). We conducted a survey of fungi colonizing chickpea stems and post-harvest residues, and selected from them two fungi which have extensive records as experimental biological control agents: Aureobasidium pullulans and Clonostachys rosea. When either of these fungi were applied in quantity to chickpea stems in the laboratory, both were able to completely suppress sexual and nonsexual reproduction of Didymella rabiei. In addition, C. rosea parasitized D. rabiei.
Technical Abstract: Fungi colonizing senescent chickpea (Cicer arietinum) stems and post-harvest debris from Pullman, WA, were enumerated and identified with the objective of finding species potentially useful for biological control of Didymella rabiei (conidial state = Ascochyta rabiei), causal agent of Ascochyta blight. In addition to D. rabiei, primary colonizers were, in order of decreasing abundance, Alternaria tenuissima, Al. infectoria, Ulocladium consortiale, U. atrum, and Epicoccum purpurascens. Present at lower frequencies were Fusarium pseudograminearum, Al. malorum, Cladosporium herbarum, Aureobasidium pullulans, Clonostachys rosea and miscellaneous anamorphic ascomycetes. On agar media and autoclaved chickpea stems, Au. pullulans consistently grew faster than A. rabiei, and excluded A. rabiei from the substrate. When stems received prior inoculation with Au. pullulans or C. rosea, followed by inoculation with compatible mating types of Didymella rabiei, pseudothecia and pycnidia of D. rabiei were suppressed. Results suggest that Au. pullulans and C. rosea can inhibit A. rabiei and its sexual stage, Didymella rabiei, on chickpea debris. C. rosea formed appressoria on, then invaded, hyphae of D. rabiei. Small scale field experiments using Au. pullulans and C. rosea have been initiated.