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• Biological control agents were tested in the field in almond, cherry, and grapevine. • Trichoderma atroviride SC1 protected efficiently grapevine pruning wounds. • Clonostachys rosea J1446 protected efficiently almond and cherry pruning wounds. The ascomycete fungi that cause wood canker diseases in perennial, horticultural crops are often generalist pathogens able to infect multiple host plants. These pathogens frequently infect pruning wounds, and the protection of such wounds with chemicals or biological control agents (BCAs) is an essential component of disease management. This study aimed at assessing four commercial BCAs for their ability to prevent almond, cherry, and grapevine pruning wound infections by three canker pathogens under field conditions for two growing seasons: Calosphaeria pulchella in cherry, Neofusicoccum parvum in almond and grapevine, and Eutypa lata in all three hosts. The two bacterial BCAs tested, Bacillus amyloliquefasciens MBI 600 and Streptomyces lydicus WYEC 108, performed poorly overall as infection rates in treated wounds were not significantly different than in the water-treated wounds for most pathogens in all crops. Trichoderma atroviride SC1 provided the best protection against E. lata and N. parvum in grapevine, achieving superior or equivalent protection than the standard conventional chemical thiophanate-methyl. Field trials also demonstrated that Clonostachys rosea J1446 provided satisfactory protection of pruning wounds against E. lata and C. pulchella in cherry and against E. lata and N. parvum in almond trees. The identification of effective BCAs for use in multiple crops and against multiple pathogens is a great step towards a sustainable management of fungal canker diseases by mitigating the negative impacts of chemical fungicides. [ABSTRACT FROM AUTHOR]

Abstract: Host specificity of plant pathogens can be dictated by genes that enable pathogens to circumvent host defenses. Upon recognition of a pathogen, plants initiate defense responses that can include the production of antimicrobial compounds such as phytoalexins. The pea pathogen Nectria haematococca mating population VI (MPVI) is a filamentous ascomycete that contains a cluster of genes known as the pea pathogenicity (PEP) cluster in which the pisatin demethylase (PDA) gene resides. The PDA gene product is responsible for the detoxification of the phytoalexin pisatin, which is produced by the pea plant (Pisum sativum L.). This detoxification activity allows the pathogen to evade the phytoalexin defense mechanism. It has been proposed that the evolution of PDA and the PEP cluster reflects horizontal gene transfer (HGT). Previous observations consistent with this hypothesis include the location of the PEP cluster and PDA gene on a dispensable portion of the genome (a supernumerary chromosome), a phylogenetically discontinuous distribution of the cluster among closely related species, and a bias in G+C content and codon usage compared to other regions of the genome. In this study we compared the phylogenetic history of PDA, beta-tubulin, and translation elongation factor 1-alpha in three closely related fungi (Nectria haematococca, Fusarium oxysporum, and Neocosmospora species) to formally evaluate hypotheses regarding the origin and evolution of PDA. Our results, coupled with previous work, robustly demonstrate discordance between the gene genealogy of PDA and the organismal phylogeny of these species, and illustrate how HGT of pathogenicity genes can contribute to the expansion of host specificity in plant-pathogenic fungi. [Copyright &y& Elsevier]

Fungi that cause grapevine trunk diseases, including Diplodia seriata , Eutypa lata , Neofusicoccum parvum , and Phaeomoniella chlamydospora , all colonize woody tissues, but lesions develop to different extents. Such variation is thought to correspond to fungal virulence, but it may also reflect host metabolic responses to limit colonization. From the woody stems of potted Vitis vinifera 'Cabernet-Sauvignon' in the greenhouse, we measured wood lesions and quantified metabolites at the lesion margins. Amino acids, sugars, phenolics, and terpenoids were quantified by appropriate chromatography techniques. At 3 months post-inoculation (MPI) lesions from P. chlamydospora and N. parvum were larger than those of D. seriata and E. lata. Among all pathogen treatments, compared to controls, lower concentrations of terpenoids at 0.5 MPI were followed at 2 MPI by higher concentrations of some phenolic compounds. Lesion length did not correlate with primary metabolites, but larger lesions did correlate with higher phenolic concentrations and lower terpenoid concentrations. • Lignicolous fungi infect grapevine pruning wounds to cause trunk diseases. • The metabolomic response to infection may help explain the wound-healing process. • In the greenhouse, we quantified metabolites in wood of inoculated grapevines. • High phenolic levels at 2 months may reflect compartmentalization of the fungi. [ABSTRACT FROM AUTHOR]