Caps analysis: A possible epidemiological approach for the study of Armillaria gallica attacks to declining oak trees

Oak decline is the result of one of the most severe forest pathogen outbreaks on a regional scale in Europe over the last decades. Among other fungal attacks observed in southern Italy, root infections have frequently been ascribed to populations of locally widespread isolates of A. gallica, a weakly pathogenic species of the genus Armillaria, which is responsible for well-known and worldwide occurring root rot and wood decay. Biomolecular techniques have been increasingly acknowledged as powerful tools in the epidemiological approach toward diseases in forest ecosystems. For this purpose, a study was carried out on the intraspecific variability of a population of 96 A. gallica isolates sampled from the "Difesa Grande" oak stand located in Gravina di Puglia (southern Italy), based on restriction fragment length polymorphism analysis of the intergenic spacer 1 region of rDNA, namely CAPS (cleaved amplified polymorphic sequence) analysis. Three different banding patterns were yielded by the isolates under study, one of which is commonly reported for this species in the literature. The other two patterns were previously detected only once within a broad-scale Italian population that we had collected before. Therefore, it can be argued that, if the DNA region analysed is more variable than what has been reported till now for A. gallica, then the biodiversity within this species is more pronounced than previously thought. Thus, new perspectives seem to emerge for a better understanding of landscape pathology dynamics concerning oak decline.