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

Abstract

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.

Mycotoxins and Other Secondary Metabolites Are Produced by Gnomoniopsis smithogilvyi When Confronted with Biological and Chemical Control Agents

“…A phylogenetic tree of the TEF-α gene is shown in Figure S1 (supplementary material). G. smithogilvyi isolates obtained in this study showed a very close relation with the isolates retrieved from the GenBank, including the type strain, as previously shown [8].…”

“…Several isolates of Gs obtained from these chestnuts were confirmed as the causal agent of chestnut brown rot and proved to be highly aggressive in chestnuts and well adapted to a wide range of temperatures, potentially resulting in extreme losses in the context of climatic changes [8].…”

“…The genomic DNA of the isolates was extracted by the SDS protocol described by Rodrigues et al [27]. The internal transcribed spacer (ITS) region of the ribosomal RNA and a portion of the translation elongation factor 1α (TEF1-α) gene were amplified by PCR and processed, as described by Possamai et al [8]. All isolates were deposited in the fungal collection at the Micoteca da Universidade do Minho (MUM) in Braga, Portugal with catalogue numbers MUM 21.76 to MUM 21.98.…”

“…For the preparation of CM, fresh and healthy chestnuts of the variety Longal were boiled in a microwave for 15 min. Afterwards, the outer shell was removed, and the cooked endosperm was blended in a proportion of 200 g per 1 L of distilled water using a domestic blender (Moulinex, Paris, France) [8]. Agar was added at 2%, and the medium was autoclaved for 121 • C for 15 min.…”

Physiological response of chestnuts (Castanea mollissima Blume) infected by pathogenic fungi and their correlation with fruit decay

“…Chestnut fruit provides favourable conditions for the invasion and reproduction of pathogens due to their high nutrient contents and strong respiratory intensity ( Possamai, Dallemole-Giaretta, Gomes-Laranjo, Sampaio, & Rodrigues, 2023 ). After being harvested, chestnuts remain viable seeds with a well-functioning defence enzyme and active oxygen-free radical clearance system.…”