Neofabraea spp. causing apple bull’s eye rot: Identification and characterization of some Italian isolates

Abstract: Bull’s eye rot, one of the main postharvest disease of apples, can be caused by four species belonging to Neofabraea (N. vagabunda, N. malicorticis, N. perennans and N. kienholzii). To verify the current causal agents of apple bull’s eye rot in Italy, a pathogen monitoring of stored apples showing bull’s eye rot symptoms was carried out from 2014 to 2016 in Emilia-Romagna in Italy. The molecular identification of 42 isolates of Neofabraea by DNA sequencing of the β-tubulin region, demonstrated the prevalence of N. vagabunda, however, the presence of N. malicorticis was also reported for the first time in Italy. In vitro assays were carried out to test the nutritional and temperature requirements of the isolates. The use of relatively low temperature (< 20 °C) was considered fundamental to favor the conidial production. The culture at 15 °C on tomato agar for 14 days provided a rapid and a reliable method to allow steady growth and favor the conidial production of N. vagabunda and N. malicorticis. A biological and morphological characterization of the isolates was performed in vitro on tomato agar, and the pathogenicity of the isolates was tested on ‘Cripps Pink’ apples. For the first time, the presence of two morphotypes of N. vagabunda was recorded. In addition, the alkalizing ability of the pathogen was demonstrated in vitro and in apple infected tissue.