Four species of Zygophiala (Schizothyriaceae, Capnodiales) are associated with the sooty blotch and flyspeck complex on apple

Abstract

Sooty blotch and flyspeck (SBFS) is a complex of fungi that cause late-season blemishes of apple and pear fruit that cosmetically damage the cuticle, which result in fruit that are unacceptable to consumers. Previous studies reported that a single, wide-host-range species, Schizothyrium pomi (presumed anamorph Zygophiala jamaicensis), caused flyspeck on apple. In the present study we compared morphology and DNA phylogeny (ITS, LSU) of 139 fungal strains isolated from flyspeck signs from 39 apple orchards in 14 midwestern and eastern states (USA). Parsimony analysis, supported by cultural characteristics and morphology in vitro, provided support to delimit the flyspeck isolates into four species of Zygophiala, two of which are known to be sexual. Three of these species are described as new. Based on DNA phylogeny, species of Schizothyrium were shown to cluster with members of the genus Mycosphaerella in the Capnodiales, having similar asci and ascospores but morphologically distinct ascomata. These data question the value of ascomatal morphology at the ordinal level, although it still appears to be relevant at the family level, delimiting the thyrothecial Schizothyriaceae from other families in the Capnodiales.

• anamorph
• plant pathology
• SBFS
• Schizothyrium pomi
• Zygophiala jamaicensis

The authors thank Dr Turner Sutton for cultures; Anne Dombroski, Khushboo Hemnani, Alicia Owens and Miralba Agudelo for technical assistance; and Dr Lois Tiffany for advice.