Novel fungal genera and species associated with the sooty blotch and flyspeck complex on apple in China and the USA

Abstract

Fungi in the sooty blotch and flyspeck (SBFS) complex cause blemishes on apple and pear fruit that result in economic losses for growers. The SBFS fungi colonise the epicuticular wax layer of pomaceous fruit but do not invade the cuticle. Fungi causing fuliginous and punctate mycelial types on apple are particularly difficult to identify based on morphological criteria because many species in the SBFS complex share the same mycelial phenotypes. We compared the morphology and nuclear ribosomal DNA phylogeny (ITS, LSU) of 11 fungal strains isolated from SBFS blemishes on apple obtained from two provinces in China and five states in the USA. Parsimony analysis, supported by cultural characteristics and morphology in vitro, provided support to delimit the isolates into three novel genera, representing five new species. Phaeothecoidiella, with two species, P. missouriensis and P. illinoisensis, is introduced as a new genus with pigmented endoconidia in the Dothideomycetes. Houjia (Capnodiales) is introduced for H. pomigena and H. yanglingensis. Although morphologically similar to Stanjehughesia (Chaetosphaeriaceae), Houjia is distinct in having solitary conidiogenous cells. Sporidesmajora (Capnodiales), based on S. pennsylvaniensis, is distinguished from Sporidesmium (Sordariomycetes) in having long, multiseptate conidiophores that frequently have a subconical, darkly pigmented apical cell, and very long, multi-euseptate conidia.

A New View of Sooty Blotch and Flyspeck

“…For example, five new generaMicrocyclosporella, Microcyclospora, Phaeothecoidiella, Houjia, and Sporidesmajora-were described, containing nine new SBFS species (22,72). Based on preliminary results from ongoing surveys of apple orchards in Turkey, Norway, Germany, Slovenia, Poland, and Brazil, it is highly likely that many additional SBFS species will be described in the next few years.…”

Scleroramularia gen. nov. associated with sooty blotch and flyspeck of apple and pawpaw from the Northern Hemisphere

“…Furthermore, a diverse range of different epiphytic fungi, representing several novel genera, has recently been reported to be associated with SBFS (Frank et al 2010;Yang et al 2010). The fact that fungi occurring in different plant parts appear to be ecologically and genetically separated suggests that as more species of fruit are sampled, we will gain a better understanding of the species associated with SBFS, their host range, distribution and ecology.…”

“…For example, Sporidesmajora, Houjia, and Phaeothecoidiella were recently distinguished from the previous "Xenostigmina," "Cercostigmina" and "Stigmina" SBFS fungi from China and the U.S. (Batzer et al 2005;Yang et al 2010). Furthermore, an investigation of SBFS fungi conducted in Germany and Slovenia resulted in naming of two additional genera, Microcyclospora and Microcyclosporella, from SBFS groups previously assigned as "Pseudocercospora" and "Pseudocercosporella" respectively (Batzer et al 2005;Frank et al 2010).…”

“…Fungi in the SBFS complex are highly diverse, comprising as many as 78 putative species based on genetic and morphological evidence; most of these (68 species) grouped within the Capnodiales, Dothideomycetes (Batzer et al 2005Díaz Arias et al 2010;Frank et al 2010;Johnson and Sutton 1994;Johnson et al 1996;Li et al 2010;Ma et al 2010, Yang et al 2010Zhai et al 2008;Zhang et al 2007Zhang et al , 2009). To date, only 24 of these species have been assigned Latin binomials.…”

“…Sooty blotch and flyspeck (SBFS) is a complex of epiphytic fungi that cause late-season blemishes on fruit with waxy cuticles in humid regions worldwide (Batzer et al 2005;Colby 1920;Williamson and Sutton 2000;Yang et al 2010). Substantial economic losses for growers can result when these blemished fruit are downgraded from freshmarket to processing uses (Colby 1920;Díaz Arias et al 2010).…”