First Report of Lecanicillium aphanocladii Causing Rot of Tremella fuciformis in China

From the paper

Abstract

The white jelly-leaf mushroom (Tremella fuciformis Berk.) is a widely consumed edible fungus in Asia, particularly in China (Stamets 2000). In 2013, fresh T. fuciformis yield reached 385,000 t from all over China. Fujian Province is the main producing area of T. fuciformis, with 358,000 t in 2013. However, in October 2015, a serious rot disease with more than 30% incidence was found on T. fuciformis at a mushroom factory in Sanming, Fujian, China (26.30°N, 118.42°E). The symptoms mainly occurred on the bottom surface of T. fuciformis. Infected fruiting bodies were covered by white mycelia that later turned red or fuchsia. In the final stages of infection, the T. fuciformis fruiting bodies turned dark red or brown before rotting. The aerial mycelium of the pathogen was isolated from surface tissues of symptomatic fruiting bodies. On potato dextrose agar (PDA), the pathogen colony appeared red, reddish, and then white to cream colored, successively. Aerial mycelia were white and grew vigorously to a height of 1 to 6 mm. Conidiophores were flask shaped, measuring 5.1 to 11.2 × 1.1 to 2.0 µm, solitary or more often two to four in whorls on each node. Conidia were borne on the tops of the branches of conidiophores and were oval to subglobose. Spores ranged from 1.3 to 2.0 µm in width and 2.1 to 4.3 µm in length, which was consistent with previous reports on the characteristics of Lecanicillium aphanocladii (Zare and Gams 2001; Pečiulytė and Kačergius 2012). Species identification was confirmed by ribosomal internal transcribed spacer (ITS) DNA sequencing. The ITS1-5.8S rRNA gene-ITS2 region was amplified from the isolated strain using primers ITS1 and ITS4 (White et al. 1990). A BLAST search in GenBank indicated the ITS sequence (NCBI accession no. KX530079) had 99% similarity to L. aphanocladii (KC574075). The pathogen was grown on PDA at 25°C in the dark for 14 days, after which the spore suspension (1 × 10⁷ conidia/ml) was prepared by flooding the agar surface with sterilized double-distilled water. Each fruiting body of T. fuciformis (48 biological replicates in total) was inoculated with three small discs of filter paper (6 mm in diameter) that had been dipped in the spore suspension; discs soaked with sterile distilled water represented the control. The inoculated fruiting bodies were maintained at 23°C and 90 to 95% relative humidity for 8 to 10 days in the mushroom factory, after which a white cottony growth was observed on the bottom surface of each fruiting body. Other symptoms also developed that were similar to those observed at the original samples. The pathogen was reisolated from infected fruiting bodies and was confirmed to be L. aphanocladii, based on morphological characteristics and the ITS sequence. Meanwhile, the control T. fuciformis grew normally without any symptoms. To our knowledge, this is the first report of the occurrence of L. aphanocladii causing rot disease on T. fuciformis, and this pathogen has been reported to infect insects (Zare and Mohammadi 2006; Pečiulytė and Kačergius 2012). It is a concern to producers of this edible fungus.