Verticillium disease of Agaricus bisporus: variations in host contribution to total fungal DNA in relation to symptom heterogeneity

Abstract

The pathogenic fungus Verticillium fungicola, responsible for dry bubble disease of the common mushroom Agaricus bisporus, causes various symptoms on its host, bubbles (undifferentiated spherical masses), bent and/or split stipes (blowout) and spotty caps. Host DNA quantification by real-time PCR was used to observed relationships between the type of symptom and the relative amount of A. bisporus and V. fungicola in diseased mushrooms. Verticillium fungicola is involved in bubble formation but does not appear to regulate its growth. Quantifications in bubbles and stipe-bubbles (morphology between bubble and sporophore with stipe blowout) showed that the pathogen has no effect on the growth of undifferentiated host hyphae but prevents morphological differentiation if not initiated and stops it when initiated hyphae are affected. Mushrooms with stipe blowout exhibiting both mature and abortive lamellae reveal that V. fungicola has a restricted area of action in host tissues. Despite their visual aspect, healthy looking parts of mushrooms showing spots or stipe blowout were actually contaminated. Discolouration and symptom development are two distinct events. The colour of the tissues was correlated to the percentage of A. bisporus DNA, suggesting that discolouration is not an efficient defensive mechanism, and occurs at the time V. fungicola developed enough to induce tissues necrosis.

Lecanicillium fungicola: causal agent of dry bubble disease in white‐button mushroom

“…The contribution of A. bisporus DNA to the total DNA of Lecanicillium‐ infected fruiting bodies is lower in infected primordia than in young bubbles, indicating that, in a developing bubble, the Agaricus mycelium expands faster than the mycelium of L. fungicola (Largeteau et al ., 2007). There is no tissue differentiation in bubbles, and stipe‐blow outs can show hymenial cavities without gills or with sterile gills.…”

“…There is no tissue differentiation in bubbles, and stipe‐blow outs can show hymenial cavities without gills or with sterile gills. This suggests that L. fungicola infection interferes with tissue differentiation of the host (Largeteau et al ., 2007). Results by Largeteau et al .…”

“…Infection at the primordium stage, in which tissue is not yet differentiated, would lead to an amorphous mass of undifferentiated mushroom tissue, whereas infection at later stages, when tissue differentiation has begun, would lead to (partially) deformed mushrooms. Largeteau et al . (2007) also proposed that L. fungicola had no effect on the growth rate of undifferentiated hyphae, because there was no correlation between the weight of the bubble and the quantity of host DNA.…”

Quantitative genetics to dissect the fungal–fungal interaction between Lecanicillium verticillium and the white button mushroom Agaricus bisporus

“…The mycoparasite affects the morphogenesis of fruiting bodies in its fungal host and this is an interesting model for studying interspecific fungal interactions and mushroom development. Infection is manifested as three types of symptoms designed bubble, stipe blow-out, and spotty cap depending on the development stage at the time of infection (Largeteau et al 2007;North & Wuest 1993). The disease is a limiting factor for mushroom production leading to yield decreases and severe economic losses.…”

Relationship between Yield Components and Partial Resistance to Lecanicillium fungicola in the Button Mushroom, Agaricus bisporus, Assessed by Quantitative Trait Locus Mapping

“…Undifferentiated spherical mass (dry bubble), stipe blowout, and spotty cap (17,21) characterize L. fungicola infection, leading to yield decreases and severe economic losses. Today, control of L. fungicola relies on prophylactic measures and the use of fungicides.…”