Genetic variation in a Chitinase gene of Beauveria bassiana: Lack of association between enzyme activity and virulence against Hypothenemus hampei

Abstract

Like other entomopathogenic fungi, Beauveria bassiana produces enzymes that degrade cuticle for penetration in the host at the time of infection. Chitinases are considered important enzymes for chitin hydrolysis, one of the main insect exoskeleton components. In this study, polymorphism in B. bassiana chitinase gene was analyzed by PCR-RFLP and compared with the enzymatic activity and mortality caused on adults of coffee berry borer, Hypothenemus hampei (Ferrari) (Coleoptera: Scolytidae). Thirty B. bassiana isolates obtained from different insect species and geographic origins were used. The activity of chitinases was not directly related with the mortality rate of each strain, emphasizing the hypothesis that the virulence is multifactorial. The chitinase gene analyses showed low variability between isolates, as only four isolates presented polymorphism. Therefore it was not possible to correlate the polymorphism with virulence and chitinolitic activity. Lack of association between chitinase gene polymorphism and enzyme activity suggests that the polymorphic region studied may not be involved in enzymatic activity of this gene. Further, lack of association between enzyme activity and virulence suggests that there may be other enzymes and factors that could contribute to infection ability. No association between polymorphism in chitinase gene with that of geographic region or origin was observed. © 2009 Academic Journals Inc.