Morphological and genetic diversity of Biscogniauxia mediterranea associated to Quercus suber in the Mediterranean Basin

Abstract

Biscogniauxia mediterranea is a widespread fungus that causes charcoal disease on cork oak and other hardwood hosts. It had been considered a secondary pathogen causing the disease only in stressed hosts. However, its frequency and severity have been increasing, inclusive in young trees without other decline signs and developing atypical symptoms. The present work aims to assess the fungus' variability in the Mediterranean basin, following cork oak geographical distribution. A collection of 36 isolates originated from cork oak in Portugal and other Mediterranean countries, from other hosts and from trees with different ages and disease expression were analyzed by cultural characteristics, conidial dimensions, and growth rates at different temperatures and by microsatellite-primed PCR profiles. Clustering UPGMA analyses combining different parameters were preformed. All the approaches revealed high level of intraspecific polymorphism among Mediterranean isolates, not allowing relating the disease development with any analyzed features. The results highlighted the variability of this fungus that induces its adaptation ability in the present worrying scenario of climatic change. All the conditions are gathered to favor the aggravation of the disease in cork oak stands.