Chestnut Brown Rot and Gnomoniopsis smithogilvyi: Characterization of the Causal Agent in Portugal

Sweet chestnut (Castanea sativa Miller) is a nutritious food with high social and economic impacts in Portugal. The fungus Gnomoniopsis smithogilvyi (syn. Gnomoniopsis castaneae) is the causal agent of chestnut brown rot, and is currently considered one of the major threats to the chestnut production chain worldwide. Considering the lack of knowledge on both the disease and the causal agent in Portugal, studies were conducted in an attempt to develop the necessary control strategies towards the mitigation of the disease in a timely way. Isolates of G. smithogilvyi were selected from three varieties of chestnut from the northeast of Portugal, and were characterized at the morphological, ecophysiological and molecular levels. Tests of pathogenicity and virulence were also developed. Gnomoniopsis smithogilvyi was confirmed as the causal agent of brown rot disease in Portuguese chestnut varieties, which showed high susceptibility. The fungus showed high adaptability to chestnut substrates. The Portuguese isolates of G. smithogilvyi are morphologically and genetically similar to those from other countries, even though some physiological variability was observed among them.