Genetic diversity of Armillaria mellea in the Rotaliana Plane

Gobbin D., De Luca F. and Pertot Il

IOBC/WPRS Bulletin: 29 (11): 47-50, 2006

In Trentino Region, in the North East of Italy, Armillaria mellea root rot is a severe and increasing problem on grapevine. In the vineyards the disease appears in patches of different dimensions. Infected areas and the incidence of the disease in a valley, called Rotaliana Plane, were evaluated. Genetic identification of individual mycelium (gent), and Geographic Information System (GIS) approach, were used to create a genets map of the area with the 56 dikaryontic isolates of A. mellea collected in 40 representative different locations (patches) of the valley. The isolates where classified in somatic incompatibility groups and RAPD polymorphisms determined with nine primer pairs. Somatic incompatibility analysis revealed the presence in the region of at least 23 different genets of A. mellea. Each genotype includes either one or many isolates. Three main groups (which include respectively 13, 8 and 6 isolates) were found. The RAPD analysis suggests that the population in the Rotaliana Plane was highly genetically polymophic: 55 genotypes were identified among the 56 collected. The phylogenetic relationship showed a distinction among three major groups (clades 1-3), where the clade 2 included the majority of the individuals and was subdivided in three clusters (2.1, 2.2 and 2.3). The vegetative incompatibility group 5 was exclusively present in clade 1, the group 3 was exclusivity of the subclade 2.1 while group 8 was mainly correlated with group 2.2. Since A. mellea spores infection of grapevine has to be considered irrelevant we hypothesise that the area was infected long time ago by A. mellea starting from several locations (forest and fruit trees, bushes, etc.)