Pilidium lythri Is Associated with Bunch Rot of Grapevine (Vitis vinifera)

Abstract

Bunch rot of Vitis vinifera is frequently caused by a complex of filamentous fungi. In a study on non-Botrytis fungi associated with bunch rot at harvest in northwestern Spain, rotting berries showing pink masses were observed in bunches of V. vinifera Albariño in one vineyard that experienced prolonged warm, moist conditions before harvest. The aim of this work was to identify the fungal species and determine its pathogenicity on grapes. Fungal isolates not corresponding morphologically to any known genus associated with bunch rot were obtained from the pink masses. Morphological and molecular phylogenetic analyses revealed that the isolates belonged to Pilidium lythri, an opportunistic pathogen causing tan-brown rot on strawberry. Most frequent non-Botrytis grape-rotting fungi at the vineyard were Penicillium brevicompactum, Penicillium expansum, and Talaromyces purpurogenus, while P. lythri had a low isolation frequency. Pathogenicity tests showed that P. lythri caused tan-brown rot in berries of the V. vinifera table grape varieties Regal Seedless and Red Globe. That P. lythri can directly infect healthy grape berries suggests that it may be a true pathogen associated with bunch rot on grapevine. Its presence on berries may contribute to postharvest decay of table and wine grapes.