Identification of resistance to cobweb disease caused by<i>Cladobotryum mycophilum</i>in wild and cultivated strains of<i>Agaricus bisporus</i>and screening for bioactive botanicals

Abstract

Outbreaks of cobweb disease are becoming increasingly prevalent globally, severely affecting the quality and yield of <i>Agaricus bisporus</i>. However, cobweb disease-resistant strains are rare, and little is known regarding the biocontrol management of the disease. Here, we isolated a pathogen from a severe outbreak of cobweb disease on <i>A. bisporus</i> in China and identified it as <i>Cladobotryum mycophilum</i> based on morphological characteristics, rDNA sequences, and pathogenicity tests. We then tested 30 <i>A. bisporus</i> strains for cobweb disease resistance by inoculating with <i>C. mycophilum</i> and evaluated the activity of different botanicals. We found that two wild strains of <i>A. bisporus</i> originating from the Tibetan Plateau in China were resistant to cobweb disease, and four commercial strains were susceptible. Yield comparisons of the inoculated and uninoculated strains of <i>A. bisporus</i> with <i>C. mycophilum</i> revealed yield losses of 6-38%. We found that seven botanicals could inhibit <i>C. mycophilum</i> growth <i>in vitro</i>, particularly <i>Syzygium aromaticum</i>, which exhibited the maximum inhibition (99.48%) and could thus be used for the further biocontrol of cobweb disease. Finally, we identified the bioactive chemical constituents present in <i>S. aromaticum</i> that could potentially be used as a treatment for <i>C. mycophilum</i> infection using Fourier transform infrared (FTIR) spectroscopy. These findings provide new germplasm resources for enhancing <i>A. bisporus</i> breeding and for the identification of botanicals for the biocontrol of cobweb disease.