Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/30/2012
Publication Date: 3/31/2013
Citation: Alderman, S.C. 2013. Survival, germination, and growth of Epichloe typhina and significance of leaf wounds and insects in infection of orchardgrass. Plant Disease. 97(3):323-328.
Interpretive Summary: Choke, caused by the fungus Epichloë typhina, causes annual yield loss up to 30% in orchardgrass seed production fields, and there are currently no controls for this disease. In a series of experiments to elucidate the how plants are infected, it was determined that surface growth of E. typhina, originating from leaf wounds, is likely the primary means for the fungus to reach susceptible buds at the base of tillers to establish infections, and that wounding agents such as mites can facilitate the infection process. This study defined how orchardgrass is infected by E. typhina, and suggests that prevention of leaf injury, or application of fungicides to protect wound sites, may provide a means of choke control in orchardgrass.
Technical Abstract: Epichloë typhina, [choke] is an important stroma-producing endophytic ascomycete that is responsible for significant yield loss in orchardgrass seed production fields. Although infections are presumed to occur through leaves and stems, details of the infection process and conditions that favor leaf infection are not well understood. The primary objective of this study was to evaluate the significance of leaf wounds in the infection of orchardgrass by E. typhina. Ascospore germination on leaves was predominantly mycelial at cut or puncture wound sites and iterative (conidiogenous) at sites without wounds. Epichloë typhina entered leaves by direct penetration or through wounds. In addition, the occurrence of mycelial growth of E. typhina at feeding sites of eriophyid mites provides the first evidence that leaf wounding agents such as mites may play an important role in supporting the growth of E. typhina on leaves. Results from this study indicate that surface growth of E. typhina, originating from leaf wounds, is likely the primary means for the fungus to reach meristematic tissues at the base of tillers and establish endophytic infections. Although there are currently no controls for E. typhina in orchardgrass, results from this study suggests that prevention of leaf injury, and application of fungicides to protect wound sites, may provide a means of E. typhina control in orchardgrass.