Evaluation of the infection process by Lecanicillium fungicola in Agaricus bisporus by scanning electron microscopy.
BACKGROUND
Lecanicillium fungicola causes dry bubble disease in Agaricus bisporus mushrooms leading to significant economic losses in commercial production.


OBJECTIVE
To monitor the infection process of L. fungicola in Brazilian strains of A. bisporus.


METHODS
The interaction between the mycelium of L. fungicola (LF.1) and three strains of A. bisporus (ABI 7, ABI 11/14 and ABI 11/21) was studied. Electron microscopy and X-ray microanalyses of vegetative growth and basidiocarp infection were evaluated.


RESULTS
Micrographs show that the vegetative mycelium of the Brazilian strains of A. bisporus is not infected by the parasite. The images show that the pathogen can interlace the hyphae of A. bisporus without causing damage, which contributes to the presence of L. fungicola during the substrate colonization, allowing their presence during primordial formation of A. bisporus. In the basidiocarp, germ tubes form within 16h of infection with L. fungicola and the beginning of penetration takes place within 18h, both without the formation of specialized structures.


CONCLUSIONS
Scanning electron microscopy enabled the process of colonization and reproduction to be observed within the formation of phialides, conidiophores and verticils of L. fungicola. The formation of calcium oxalate crystals by the pathogen was also visible using the X-ray microanalysis, both at the hyphae in the Petri plate and at basidiocarp infection site.
Universidade Federal de Lavras, 37200-000 Lavras, MG, Brazil.
Janaira
J
Santana Nunes
Universidade Federal de Lavras, 37200-000 Lavras, MG, Brazil.
Manuela
M
Rocha de Brito
Universidade Estadual Paulista (UNESP), Faculdade de Ciências Agrárias e Tecnológicas, Câmpus de Dracena, 17900-000 Dracena, SP, Brazil.
Diego
D
Cunha Zied
Universidade Federal de Lavras, 37200-000 Lavras, MG, Brazil.
Eloisa
E
Aparecida das Graças Leite
Universidade Federal de Lavras, 37200-000 Lavras, MG, Brazil.
Eustáquio
E
Souza Dias
Universidade Federal de Lavras, 37200-000 Lavras, MG, Brazil. Electronic address: ealves@dfp.ufla.br.
Eduardo
E
Alves
D000364:Agaricus / Q000648:ultrastructure*; D006999:Hypocreales; D008855:Microscopy, Electron, Scanning
Micopatógeno; Microanálisis de rayos X; Microscopia electrónica; Mushroom; Mycopathogen; Scanning electron microscopy; Seta; X-ray microanalyses