Genetic variations in Spanish isolates of <I>Phaeomoniella chlamydospora</I>, the causal etiological agent of Petri disease of grapevine

Abstract

Petri disease is currently considered as one of the most important mycoses of grapevine wood in terms of its incidence and extent, causing young grapevine decay in numerous vine-producing areas worldwide. One of its causal agents is the ascomycete Phaeomoniella chlamydospora (W. Gams, Crous, M. J. Wingfield & Mugnai) Crous & W. Gams. Recently, several studies focusing on the genetic and variability of this species have reported that its genetic variability is low. However, studies on the intraspecific characterisation of P. chlamydospora by other than molecular means are scarce. In this study, 57 Spanish isolates of P. chlamydospora were characterised by integrating data from morphological, pathogenic, cytological and ecological techniques. It was found that there was a relationship between the high polymorphism in these isolates (melanised, intermediate and albino cultures), and a number of groups, distinguished by their nuclear number, pathogenicity or survival in soil. The non-melanised phenotypes were associated with less virulent strains, generally possessing mono- or binucleate hyphae with low survival in soils, whilst melanised, multinucleate isolates were more virulent and survived up to 12 months in grapevine soils under laboratory conditions. Using these other criteria to distinguish forms of this pathogen, should make it easier to detect hypovirulent or non-pathogenic isolates and to advance our understanding of the biology of the fungus, especially its modes of dispersal or its ecological range in the field. The adoption of these criteria should also make it easier to characterise intraspecific variations in those cases where the genetic methods do not reflect them, as with P. chlamydospora.