Green Mold Diseases of Agaricus and Pleurotus spp. Are Caused by Related but Phylogenetically Different Trichoderma Species

Abstract

Producers of champignon (Agaricus bisporus) and oyster mushroom (Pleurotus ostreatus) are facing recent incidents of green mold epidemics in Hungary. We examined 66 Trichoderma strains isolated from Agaricus compost and Pleurotus substrate samples from three Hungarian mushroom producing companies by a polymerase chain reaction-based diagnostic test for T. aggressivum, sequence analysis of the internal transcribed spacer region 1 (ITS1) and ITS2 and (selectively) of the fourth and fifth intron of translation elongation factor 1alpha (tef1alpha), and restriction fragment length polymorphism of mitochondrial DNA. Seven Trichoderma species were identified: T. aggressivum f. europaeum (17 isolates), T. harzianum (three isolates), T. longibrachiatum (four isolates), T. ghanense (one isolate), T. asperellum (four isolates), T. atroviride (nine isolates), and a still undescribed phylogenetic species, Trichoderma sp. DAOM 175924 (28 isolates). T. aggressivum f. europaeum was exclusively derived from A. bisporus compost, whereas Trichoderma sp. DAOM 175924 exclusively occurred in the substrate for Pleurotus cultivation. Sequences of the latter strains were co-specific with those for Trichoderma pathogens of P. ostreatus in Korea. The widespread occurrence of this new species raises questions as to why infections by it have just only recently been observed. Our data document that (i) green mold disease by T. aggressivum f. europaeum has geographically expanded to Central Europe; (ii) the green mold disease of P. ostreatus in Hungary is due to the same Trichoderma species as in Korea and the worldwide distribution of the new species indicates the possibility of spreading epidemics; and (iii) on mushroom farms, the two species are specialized on their different substrates.

The First Report on Mushroom Green Mould Disease in Croatia / Prvi Izvještaj O Bolesti Zelene Plijesni U Hrvatskoj

“…At the same time, in the cultivation of button mushroom the sole isolated pathogen was T. harzianum. These results add a new name to the list of the potential mushroompathogenic Trichoderma species, as earlier studies from other countries identifi ed only T. aggressivum as the button mushroom pathogen (11,12). This fi nding suggests a continuous evolving of green mould disease in cultivated mushrooms and underlines the importance of monitoring these infections.…”

“…Aggressive biotypes had originally been identifi ed as Trichoderma harzianum Th2 and Th4, but later they were re-described on the basis of morphological characteristics and of the phylogenetic analyses of the internal transcribed spacer (ITS) 1 region and the translation elongation factor 1-alpha (tef1) gene as new species T. aggressivum f. europaeum and T. aggressivum f. aggressivum, respectively (11). Agaricus green mould reported in Hungary seems to have been caused by Trichoderma aggressivum f. europaeum (12).…”

“…Recently, green mould disease of cultivated oyster mushroom has also been reported in several countries (12)(13)(14)(15)(16)(17)(18), and the causal agents were identifi ed and described as new species T. pleurotum and T. pleuroticola (19,20).…”

“…The effect of temperature, natural compounds, and commercial fungicides on the mycelial growth of two isolates from each species in comparison with their host mushrooms were tested on solid YEG medium (12). The fungi were inoculated onto the solid surface as mycelial plugs (4 mm diameter) taken from the actively growing edge of young colonies.…”

Detection of fungi using a long-period fibre grating

“…In spite of a number of benefits provided by utilization of biofungicides as bioagents, they also pose a serious, even lethal, threat to some immuno-compromised and immuno-suppressed humans. Moreover, a well-known Trichoderma species have been reported as a source causing a green-mould disease in plants [16][17][18][19]. As a consequence, fast and reliable detection of fungi can be a boon to the agriculture industry.…”