Submitted to: Journal of Phytopathology
Publication Type: Abstract Only
Publication Acceptance Date: 2/27/2002
Publication Date: 3/31/2002
Citation: Dugan, F.M., Lupien, S.L. 2002. Incidence and competitive interactions of botrytis cinerea and other filamentous fungi quiescent in grape berries and dormant buds in central washington state. Journal of Phytopathology. 92(supplement):S21-S22. Interpretive Summary: Botrytis cinerea, the gray mold fungus, causes bunch rot of grapes. The fungus is known to exist quiescently in non-symptomatic, young grape berries and in over-wintered dormant buds. That these quiescent infections, especially in berries, can lead to bunch rot is accepted in the literature, but the incidence of these quiescent infections has never been quantified in the increasingly important vineyard country of central Washington state. We demonstrated that B. cinerea does indeed exist quiescently in berries in central Washington, albeit at lower levels than have been reported for some other geographic locales, and that infection in dormant buds also occurs. However, quiescent infections by other common fungi are far more frequent than infections by Botrytis. These other fungi (Alternaria, Cladosporium, Ulocladium and Aureobasidium) rot grape berries much more slowly than Botrytis, and when occupying a wound in advance of Botrytis will considerably retard the development of rot. It is plausible that these other common fungi are usually sufficiently established so that Botrytis is less able to invade berries and/or progress to bunch rot, but this hypothesis has not been rigorously tested.
Technical Abstract: Recovery of quiescent fungi from surface-disinfested, non-symptomatic grape berries and dormant buds demonstrated dominance of Alternaria, Aureobasidium,Cladosporium and Ulocladium. Up to 78% of berries were colonized prior to harvest. Botrytis cinerea was recovered from 0.2-0.5% of berries just after fruit set, and 1.6-4.8% of over-wintered dormant buds. In laboratory inoculations of mature berries with Alternaria alternata, A. infectoria, Aureobasidium pullulans, Cladosporium herbarum, C. cladosporioides, Ulocladium atrum and B. cinerea, only Botrytis was aggressive in rotting berries. Inoculations with B. cinerea alone, and in combination with the other species, demonstrated that prior occupation of wounds by the other species resulted in reduced lesion size compared to inoculation with Botrytis alone. We hypothesize that common, naturally occurring fungi constrain establishment of bunch rot via niche exclusion.