Effects of fluorescent Pseudomonas spp. isolated from mushroom cultures on Lecanicillium fungicola

Abstract

Dry bubble disease, caused by Lecanicillium fungicola, is a serious economic problem in the cultivation of the white button mushroom. Biological control of the disease would meet the mushroom industry’s efforts to minimize the use of chemicals. A total of 160 bacterial strains were isolated from colonized casing and screened for in vitro antagonism of L. fungicola. Fifty-three isolates inhibited L. fungicola in vitro. Using BOX-PCR, the 53 antagonistic isolates were grouped in 18 unique genotypes. Further characterization based on the 16S rDNA identified all isolates as Pseudomonas spp. Using previously characterized Pseudomonas isolates and their mutants it was determined that L. fungicola is sensitive to both siderophore-mediated competition for iron and production of antibiotics. However, when tested for disease suppression, none of the Pseudomonas spp. strains isolated from colonized casing effectively controlled dry bubble disease. The insensitivity of dry bubble disease to direct biological antagonism and the implications for biological control of mushroom diseases are discussed.