Cryptococcus adeliensis inciting branch canker on stone fruit trees

Abstract

Stem and branch cankers of stone fruits are among the most destructive diseases throughout stone fruit growing areas of the world, including Iran. Symptoms similar to those produced by Pseudomonas syringae pv. syringae were observed on stone fruit trees in several fruit growing areas in the Khorasan province in North Eastern Iran in 2011 and 2012. The isolates (48) recovered from almost all affected tissues had cream to pinkish, circular, glistening, pasty and convex colonies with entire margins on sucrose nutrient agar (SNA). A number of isolates induced a hypersensitive (HR)-like reaction in tobacco (Nicotiana tabacum) 11 days after infiltration of leaves with a turbid cell suspensions thereof. Pathogenicity of representative isolates (seven of 48) was confirmed by inoculation of peach (Prunus persica) twigs with a lightly turbid cell suspension of each. Blast analysis of the ITS-sequences of representative isolates revealed their 100 % homology with those of Cryptococcus adeliensis isolates present in GenBank. Analysis of fatty acid methyl esters, partial sequences of 26SrRNA and RPB2 as well as their phenotypic characteristics verified the identity of the yeast isolates as C. adeliensis. The stem canker caused by C. adeliensis appears to be a newly emerged disease of stone fruit trees.