Charcoal canker (Biscogniauxia mediterranea) in cork oak decline in Portugal

Doutoramento em Engenharia Florestal e dos Recursos Naturais - Instituto Superior de AgronomiaCharcoal canker is a disease caused by Biscogniauxia mediterranea that affects Quercus suber and other hardwood species. The fungus develops endophytically in the hosts becoming pathogenic under stress conditions. However, it has become more frequent, particularly in young trees expressing atypical symptoms. This work intends to clarify the agent involved in these disease outbreaks and its variability in different situations, as well as dispersion in natural conditions. The fungal anamorph was identified as Nodulisporium sp. in young hosts. In the stands, ascospores airborne dispersal is predominant, occurring after precipitation periods, and vertical contamination of plants doesn’t happen. A collection of isolates obtained from cork oak in Portugal and other Mediterranean countries, from other hosts and from trees with different ages and disease expression were analyzed by microsatellite-primed PCR, multigene sequencing, morpho-cultural characteristics and growth rates at different temperatures. All the approaches revealed high level of intraspecific polymorphism among isolates, not allowing relating the disease development with any considered feature. The results highlighted the variability and adaptation ability of this fungus in special in the Mediterranea region, in the present worrying scenario of climatic change. All the conditions are gathered to favor the aggravation of the disease in cork oak stand