First Report of Dactylonectria torresensis Causing Black-Foot Disease on Grapevines in the Czech Republic

Fungal Trunk Diseases Causing Decline of Apricot and Plum Trees in the Czech Republic

Fungal trunk diseases (FTDs) have been a significant threat to the global stone fruit industry. FTDs are caused by a consortium of wood-decaying fungi. These fungi colonize woody tissues, causing cankers, dieback, and other decline-related symptoms in host plants. In this study, a detailed screening of the fungal microbiota associated with the decline of stone fruit trees in the Czech Republic was performed. The wood fragments of plum and apricot trees showing symptoms of FTDs were subjected to fungal isolation. The partial internal transcribed spacer region, partial beta-tubulin, and translation elongation factor 1-α genes were amplified from genomic DNA extracted from fungal cultures. All isolates were classified, and the taxonomic placement of pathogenic strains was illustrated in phylogenetic trees. The most abundant pathogenic genus was Dactylonectria (31%), followed by Biscogniauxia (13%), Thelonectria (10%), Eutypa (9%), Dothiorella (7%), Diplodia (6%), and Diaporthe (6%). The most frequent endophytic genus was Aposphaeria (17%). The pathogenicity of six fungal species (Cadophora daguensis, Collophorina africana, Cytospora sorbicola, Dothiorella sarmentorum, Eutypa lata, and E. petrakii var. petrakii) to four Prunus spp. was evaluated, and Koch's postulates were fulfilled. All tested isolates caused lesions on at least one Prunus sp. The most aggressive species was E. lata, which caused the largest lesions on all four tested Prunus spp., followed by E. petrakii var. petrakii and D. sarmentorum. Japanese plum (Prunus salicina) and almond (P. amygdalus) were the most susceptible hosts, while apricot (P. armeniaca) was the least susceptible host in the pathogenicity trial.

Lignans Extract from Knotwood of Norway Spruce—A Possible New Weapon against GTDs

Grapevine trunk diseases (GTDs) pose a major threat to the wine industry worldwide. Currently, efficient biological methods or chemical compounds are not available for the treatment of infected grapevines. In the present study, we used an extract from the knotwood of spruce trees as a biological control against GTDs. Our in vitro trial was focused on the antifungal effects of the extract against the most common GTD pathogens—Cadophora luteo-olivacea, Dactylonectria torresensis, Diaporthe ampelina, Diaporthe bohemiae, Diplodia seriata, Eutypa lata, and Phaeoacremonium minimum. Our in vitro trial revealed a high antifungal effect of the extract against all tested fungi. The inhibition rates varied among the different species from 30% to 100% using 1 mg·mL⁻¹ extract. Subsequently, the efficiency of the extract was supported by an in planta experiment. Commercial grafts of Vitis vinifera were treated with the extract and planted. The total genomic DNA of grapevines was extracted 10 days and 180 days after the treatment. The fungal microbial diversities of the treated/untreated plants were compared using high-throughput amplicon sequencing (HTAS). Treated plants showed 76.9% lower relative abundance of the genus Diaporthe and 70% lower relative abundance of the genus Phaeoacremonium 10 days after treatment. A similar scenario was observed for the genus Cadophora 180 days after treatment, where treated plants showed 76% lower relative abundance of this genus compared with untreated grapevines.

Detection and identification of “black foot” pathogens of grapes in Crimea

At the present stage of development, stable economic efficiency of viticulture is possible if a decrease in the viability of grape plants, accompanied by a decrease in their productivity and lifecycle reduction, is prevented. Progressive grapevine weakening can be caused by both climate change and affection of perennial wood by the complexes of phytopathogenic fungi. In the last two decades, in all major grape-cultivating states, the root rot or “black foot” of grapes has been attributed to the most harmful diseases of perennial wood, especially in nurseries and young plantations. Presently, 30 fungal species are known to be associated with this disease, with the most common genera being Campylocarpon, Cylindrocladiella, Dactylonectria, Ilyonectria, Neonectria, Pleiocarpon, and Thelonectria. The article presents the results of laboratory researches and field experiments aimed at studying the etiology of inhibition of grape plant development in the conditions of Crimea. For the period from 2017 to 2021, in the vineyards of Mountain-Valley, South-Western and Central-Steppe Crimea, the affection of bushes of grape varieties ‘Moldova’, ‘Aligote’, ‘Arcadia’, ‘Lora’, ‘Rkatsiteli’ with the disease "black foot" or root rot of grapes was diagnosed for the first time. Using of molecular biological approach based on the polymerase chain reaction (PCR) made it possible to establish that “black foot” pathogens in Crimean vineyards include Dactylonectria macrodidyma (Halleen, Schroers & Crous) L. Lombard & Crous, 2014 and Ilyonectria destructans (Zinssm.) Rossman, L. Lombard & Crous, 2015.