Extensive colonization of apples by smut anamorphs causes a new postharvest disorder

Abstract

Colonization of apples by ballistoconidium-forming fungi causes a new disorder, here named 'white haze'. White haze may occur in mild form in the field, but only becomes problematic after Ultra-Low Oxygen storage, and, therefore, may be considered as a postharvest disorder. All isolates, obtained using the spore-fall method, were morphologically identified as anamorphs of smut fungi belonging to the genus Tilletiopsis. Sequence analysis of the D1/D2 and the ITS domains of the rDNA revealed nine novel taxa scattered among the Exobasidiomycetidae (Ustilaginomycetes). Field experiments confirmed the erratic incidence of white haze over the years, and the development of the disorder seems to be enhanced at lower temperatures and a high relative humidity. Several scab fungicide treatments showed diminishing effects on the incidence of white haze.