Various Population Structures of Cryphonectria parasitica in Cáceres (Spain) Determine the Feasibility of the Biological Control of Chestnut Blight with Hypovirulent Strains

Abstract

Chestnut blight, caused by Cryphonectria parasitica, is a severe disease that may be biologically controlled by the use of hypovirulent strains, but the diversity of the pathogen population affects biocontrol feasibility. Villuercas–Ibores–Jara, the Jerte Valley and La Vera are the main chestnut production districts in Cáceres (central-western Spain). The purpose of this study is to determine the Vegetative Compatibility Groups (VCGs) and mating types in these districts and to identify hypovirulent isolates to be used in biological control. The VCGs were determined by the merging/barrage response; PCR tests were used for the mating type determination and CHV-1 hypovirus detection. In total, 40 sites were surveyed and 269 isolates were obtained, most of them (227) from the Villuercas–Ibores–Jara district, where EU11 was the predominant VCG (88.1%) with EU1 (6.6%) and EU12 (4.4%) being also present. In the Jerte Valley and La Vera, EU1 (61.9%), EU11 (11.9%) and EU12 (11.9%) were the predominant VCGs. Both mating types were detected (48% MAT-1; 50% MAT-2) and in general, only one mating type was found in each site. The presence of Cryphonectria hypovirus 1 (CHV-1), subtype I, was identified in only one isolate (VCG EU11) from Villuercas–Ibores–Jara. The characteristics of the C. parasitica population in this district and the occurrence of CHV-1 hypovirus support the potential of successful biological control in Villuercas–Ibores–Jara using hypovirulent strains, while in the Jerte Valley and La Vera only preventive measures are recommended.

Spanish ecological battleground: population structure of two invasive fungi, Cryphonectria parasitica and Fusarium circinatum

“…2) C. parasitica has been introduced in one of the neighboring regions and, from there, has arrived in Cantabria (or vice versa). In contrast, a study from Southern Spain showed that EU-1 was not the main VC type and made up only 6.6% of total isolates (Rodrıǵuez-Molina et al, 2023). Therefore, the Cantabrian populations appeared similar to other North Spanish populations but not the Southern populations.…”

“…Since the genetic diversity of the fungus is not very high in Europe, biocontrol still seems a viable option. For example, both mating types were found in Southern Spain also, but they were detected in different locations, which means sexual reproduction among them is unlikely (Rodrıǵuez-Molina et al, 2023). Nevertheless, increasing genetic diversity could make biocontrol less efficient in European populations with high genetic diversity, such as Italy, France, and Switzerland.…”

Forecasting of Airborne Conidia Quantities and Potential Insect Associations of Cryphonectria parasitica, the Causal Agent of Chestnut Blight, in England

“…Planting stock, timber, and bark are pathways of long-distance dispersal [ 5 ]. This pathogen is considered for its detrimental impact on forestry and agricultural orchards for nut production [ 6 ] and is a protected-zone quarantine pest in the EU according to the Commission Implementing Regulation 2019/2072.…”