Trichoderma species associated with green mould disease of Pleurotus ostreatus and their sensitivity to prochloraz

Abstract

Green mould disease causes serious economic losses in Pleurotus ostreatus crops worldwide, including in Italy, where prochloraz is the only chemical fungicide allowed to control the disease. The effectiveness of the doses 0.01, 0.05, 0.25 and 1.25 μL L−1 (field dose) of prochloraz (Sponix Flow, 450 g L−1), against colony growth rate and spore germination of Trichoderma pleuroti, T. pleuroticola and T. guizhouense strains on wheat straw extract agar plates were evaluated. Complete inhibition of Trichoderma pleuroti and T. pleuroticola growth was shown by the field dose of prochloraz, and also by the 0.25 μL L−1 dose for T. pleuroti. Complete inhibition of spore germination occurred for all Trichoderma strains at field dose, and at 0.25 μL L−1 for T. pleuroti strains. In in vivo assays, the effect of prochloraz doses 0.05, 0.25 and 1.25 μL L−1 on colonization of straw substrate by T. pleuroti, T. pleuroticola and T. guizhouense inoculated at two spore densities (102 and 105 spores mL−1) immediately after P. ostreatus spawn was studied. Trichoderma pleuroti and T. pleuroticola were both responsible for green mould disease, whereas T. guizhouense was not pathogenic. Trichoderma pleuroti was more aggressive than T. pleuroticola. Prochloraz was effective against T. pleuroti at the field dose, and against T. pleuroticola at 0.25 and 1.25 μL L−1. The study on Trichoderma × Pleurotus interaction type showed that Trichoderma species were active against the mycelial growth of P. ostreatus by competition for space and nutrients, and neither hyphal interaction nor effect by volatile or nonvolatile metabolites occurred.

Four new species of Trichoderma in the Harzianum clade from northern China

“…Several studies have confirmed that species in this clade are important because of their mycoparasitism ( Chaverri et al 2015 ; Chen and Zhuang 2017a ; Sun et al 2019). When numerous biological control agents were explored deriving from species in the Harzianum clade ( Chaverri et al 2015 , several taxa, such as T. atrobrunneum T. pleuroti , and T. pleuroticola were recognized as causing agents of “Green mold” disease of cultivated mushroom ( Innocenti et al 2019 ; Sun et al 2019a , b ). In this study, T. lentinulae was isolated from a fruiting body and the cultivated substrates of L. edodes , causing the decay of the host as well.…”

“…Preliminary BLAST searches with ITS , RPB2 , and TEF1-α gene sequences of the new isolates against NCBI, TrichOKey (Druzhinina and Kopchinski 2006), and TrichoBlast ( Kopchinskiy et al 2005 ) databases identified species closely related to our isolates. Based on this information, sequences of ITS , RBP2 , and TEF1-α of 133 strains, representing 59 species were downloaded from GenBank, following recent publications ( Qin and Zhuang 2017 ; Qiao et al 2018 ; Innocenti et al 2019 ). Among them, 139 strains are belonging to the Harzianum clade, and Trichoderma ceramicum , T. parestonicum , and T. estonicum were chosen to represent the outgroup.…”

“…Species of this genus have been widely used in the biocontrol of plant pathogens ( Chaverri et al 2015 ; Degenkolb et al 2015 ; Bunbury-Blanchette and Walke 2019) and production of enzymes and bioactive compounds ( Sun et al 2016 ). Nevertheless, some of them are associated with green mold diseases in the commercial production of mushrooms ( Innocenti et al 2019 ; Sun et al 2019a ) . Morphologically, the asexual-morphs are similar in producing branched tree-like conidiophores with cylindrical to nearly subglobose phialides and ellipsoidal to globose conidia, but their variation is insufficient to differentiate the Trichoderma species ( Chaverri et al 2015 ; Qin and Zhuang 2017 ; Qiao et al 2018 ).…”

“…Multilocus molecular phylogeny, based on combined sequence data of the internal transcribed spacer ( ITS ) regions, RNA polymerase II subunit ( RPB2 ), and the translation elongation factor 1-α gene ( TEF1-α ), enables rapid and accurate identification of the Trichoderma species ( Druzhinina et al 2005 ; Atanasova et al 2013 ; Chaverri et al 2015 ). Currently, the combination of multi-gene phylogenetic analysis and phenotypic characteristics is extensively applied in species delimitation of Trichoderma ( du Plessis et al 2018 ; Qiao et al 2018 ; Innocenti et al 2019 ).…”

“… Trichoderma harzianum Rifai is one of the most well-known Trichoderma species, due to its antifungal properties and effective bio-control ability, used to suppress soil-borne plant pathogens ( Chaverri et al 2015 ; Degenkolb et al 2015 ; Bunbury-Blanchette and Walker 2019 ). As a cosmopolitan and ubiquitous fungus, it has been isolated from diverse substrates, such as soil, plant tissue, and mushrooms ( Chaverri et al 2015 ; Jaklitsch and Voglmayr 2015 ; Innocenti et al 2019 ; Sun et al 2019b ). Since Chaverri et al (2015) provided a systematic revision of species in the Harzianum clade, numerous new species have been described ( Jaklitsch and Voglmayr 2015 ; Qin and Zhuang 2016a ; Sun et al 2016 ; Chen and Zhuang 2017b ; Qiao et al 2018 ).…”