Diversity of Cladobotryum mycophilum isolates associated with cobweb disease of Agaricus bisporus in the south African mushroom industry

Abstract

Cladobotryum species and strain diversity of isolates collected from cobweb symptomatic Agaricus bisporus or infected casing soil were investigated due to increased incidences of the disease in the South African mushroom industry. Samples were collected from mushroom farms located in Gauteng, the Western Cape and KwaZulu Natal Provinces of South Africa.Moreover, cobweb disease isolates from the USA and Ireland were included in the study as reference cultures. Isolates were characterised using culture and conidia morphology and were identified as Cladobotryum mycophilum. The isolates were characterised by rapid colony growth between 48 and 72 h on malt extract agar and potato dextrose agar, all but two isolates (GP-15 and KZN-2) produced the pink colour of aurofurasin. All isolates could infect A. bisporus fruiting bodies with varying degrees of aggressiveness. Isolates were sequenced for their ITS, and BLAST analysis showed highest similarity (99-100%) to several ITS sequences of Hypomyces odoratus/C. mycophilum for 35 of the isolates except for one from Ireland that was identified as H. rosellus/C. dendroides. Phylogenetic analysis of the isolates showed South African cobweb disease of mushrooms to be caused by a wide diversity of strains some of which may have originated from elsewhere in the world.

Mycoparasite Hypomyces odoratus infests Agaricus xanthodermus fruiting bodies in nature

“…Further symptoms linked to cobweb disease are brown spotting on caps instigated by germinating spores (Bhatt and Singh 2002 ; Potočnik 2006 ; Parrag et al 2014 ; Carrasco et al 2017 ). In recent time, other Cladobotryum species (mainly C. mycophilum , teleomorph Hypomyces odoratus ; C. varium , teleomorph Hypomyces aurantius ) have more often been reported to cause cob-web diseases including cap spotting and patching on A. bisporus (McKay et al 1999 ; Grogan and Gaze 2000 ; Back et al 2010 , 2012b ; Lee et al 2011 ; Sharma et al 2015 ; Carrasco et al 2016 , 2017 ; Chakwiya et al 2019 ). According to McKay et al ( 1999 ), Grogan ( 2006 ) and Tamm and Põldmaa ( 2013 ), when H. odoratus occurs in mushroom farms, it is quite often misidentified under the name H. rosellus .…”

“…While attention is paid on pathogen infections in commercial mushroom cultures due to the high economic interest, infection events observed in nature are scattered and usually not deeply described. In nature, an association with basidiomycete fruiting bodies and verticillium-like anamorphs (conidiophores are verticillate with whorls of few to several phialides which give rise to the phialoconidia) can help to identify potential mycopathogens (Gray and Morgan-Jones 1980 ; Zare and Gams 2008 ; Rogerson and Samuels 1989 , 1993 , 1994 ; Põldmaa and Samuels 1999 ; Põldmaa 2003 ; Tamm and Põldmaa 2013 ; Chakwiya et al 2019 ). From the wild, L. fungicola has been isolated from fruiting bodies of Agaricales (e.g.…”

Screening and Evaluation of Essential Oils from Mediterranean Aromatic Plants against the Mushroom Cobweb Disease, Cladobotryum mycophilum

“…W. Gams & Hooz., is found in all mushroom-growing countries worldwide. The disease is prevalent especially in white button mushroom (Agaricus bisporus (Lange) Imbach) [1][2][3][4][5], king oyster mushroom (Pleurotus eryngii (DC.:Fr.) Quél.)…”

Cladobotryum mycophilum as Potential Biocontrol Agent

“…W. Gams and Hooz (teleomorph Hypomyces odoratus G.R.W. Arnold), is one of the most serious diseases affecting white button mushroom (Agaricus bisporus (Lange) Imbach) cultures worldwide [1][2][3][4]. Its occurrence generally reduces the production and quality, and thus generates economic losses because of mainly cap spotting, the reduction of crop surface and the necessity of early crop termination when the disease becomes epidemic [5].…”

“…and Trichoderma spp., have led to numerous studies on these fungi as biological control agents [14]. Most species of the Cladobotryum genus are characterised by rapid growth and colonisation of the parasitic basidiomycete [4]. Considering their high mycoparasitic capacity, these species are potential candidates for use as biological control agents against key agricultural phytopathogens.…”