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.

A New View of Sooty Blotch and Flyspeck

“…When techniques of molecular genetics were coupled with traditional morphologybased mycological methods, a far more diverse picture began to emerge. Two surveys, encompassing 39 apple orchards in 14 eastern U.S. states, documented that the SBFS complex included at least 60 putative species (3,4,18; Sidebar 2), compared to four species in 1997 (Table 1). These new species belonged to two classes of Ascomycetes, of which the class Dothideomycetes accommodated the vast majority, primarily within the order Capnodiales (17,18,54).…”

“…Although no direct evidence was presented for making this connection, it persisted as an accepted fact in the SBFS literature (2,70) until a recent study (3) showed that conidial morphology of S. pomi is distinct from that described for Z. jamaicensis (41). This discrepancy strongly suggests that Z. jamaicensis and S. pomi are separate but closely related species rather than anamorph/teleomorph stages of the same species (3).…”

Chaetothyrina mangiferae sp. nov., a new species of Chaetothyrina

“…Infected fruits are generally rejected by the market and consumers, resulting in considerable economic loss to growers , Miñarro et al 2012, Zhang et al 2015. The SBFS complex is estimated to comprise 60-80 species (Batzer et al 2005, Díaz Arias et al 2010, most are either taxonomically undetermined or undescribed (Batzer et al 2008, Sun et al 2008, Schoch et al 2009, Yang et al 2010.…”

The rise of Ramularia from the Mycosphaerella labyrinth

“…Early molecular work based on ITS DNA sequencing indicated that Mycosphaerella was monophyletic, although the subsequent introduction of additional loci and more taxa showed it was polyphyletic ( Crous et al, 2009a andCrous et al, 2009c). As a consequence, members of this genus were allocated to different families such as Schizothyriaceae ( Batzer et al 2008), Cladosporiaceae ( Schubert et al, 2007, Dugan et al, 2008, Bensch et al, 2010and Bensch et al, 2012, Dissoconiaceae, Mycosphaerellaceae and Teratosphaeriaceae ( Crous et al, 2009b andLi et al, 2012). From these results it became evident that the mycosphaerella-like morphology had evolved multiple times and a new circumscription of Mycosphaerella was urgently required.…”