Characterization of fungal species involved in white haze disorder on apples in Northern Italy and description of Golubevia mali sp. nov. and Entyloma mali sp. nov.

Abstract

White haze, caused by an extensive fungal colonization of the apple surface, is an emerging postharvest issue in several European apple production areas. It results in compromised quality and decreased marketability of the fruits, leading to economic losses. In this study, the occurrence and the diversity of white haze-related fungi associated with apples was investigated in Northern Italy. Fungal strains were isolated from apple tissues and the species diversity was assessed using molecular and phylogenetic tools. Moreover, the ability of the isolated species to reproduce symptoms on healthy apples artificially inoculated was tested. Seventy-two fungal isolates were collected. Six species belonging to different basidiomycetous genera (Entyloma, Golubevia, Tilletiopsis) were identified, showing high diversity of fungi involved in white haze development in Northern Italy. The strains were identified as E. belangeri, E. randwijkense, G. pallescens, T. washingtonensis. Moreover, two new species, E. mali sp. nov. and G. mali sp. nov. were described. The most frequently isolated strains were inoculated on healthy apple fruit, showing to be able to reproduce symptoms on red-skin apples, fulfilling Koch's postulates. This work provides new insights to increase knowledge about the causal agents of white haze on apple. In addition, the names Golubevia, Golubeviaceae and Golubeviales have been nomenclaturally validated.