Resistance Sources to Brown Blotch Disease (Pseudomonas tolaasii) in a Diverse Collection of Pleurotus Mushroom Strains

Abstract

Brown blotch disease (BBD) caused by <i>Pseudomonas tolaasii</i> is one of the most devastating diseases of <i>Pleurotus</i> spp. worldwide. Breeding for resistant strains is the most effective method for controlling BBD. To identify resistant germplasm for BBD management, 97 strains comprising 21 <i>P.</i> cf. <i>floridanus</i>, 20 <i>P. ostreatus,</i> and 56 <i>P. pulmonarius</i> were screened by two different methods; namely, inoculation of the pathogen on the mushroom pileus (IMP) and on the spawned substrate (IMSS) under controlled conditions. Out of the 97 strains screened, 22 <i>P. pulmonarius,</i> and four <i>P.</i> cf. <i>floridanus</i> were moderately resistant to BBD using the IMP method. Eleven <i>P. pulmonarius,</i> six <i>P</i>. cf. <i>florida,</i> and one <i>P. ostreatus</i> strains were highly resistant to BBD using the IMSS method. All of the 97 strains showed varying degrees of susceptibility using the IMP method, but eight strains were completely resistant using the IMSS method. Combining these two methods, five strains were highly resistant (four <i>P. pulmonarius</i> and one <i>P.</i> cf. <i>floridanus</i>) and 11 were moderately resistant (eight <i>P. pulmonarius</i> and three <i>P.</i> cf. <i>floridanus</i>). The resistance sources to <i>P. tolaasii</i> identified in <i>P. pulmonarius</i> and <i>P.</i> cf. <i>floridanus</i> could be used for further breeding of <i>Pleurotus</i> spp.