Identification and characterization of Trichoderma species from vineyards in British Columbia and studies on their potential use as biological control agents against the grapevine trunk disease Botryosphaeria dieback

One of the most important biotic factors limiting grapevine health around the world is grapevine trunk diseases (GTD). Fungal pathogens responsible for GTD infect vines mainly through pruning wounds and cause an overall decline and eventual death of the plant. Currently, there are no chemical fungicides nor biological control agents (BCA) registered in Canada for the control of GTD. Species of Trichoderma are capable of promoting grapevine health and can also protect vines by actively antagonizing plant pathogenic fungi, including GTD pathogens, through several modes of action. Accordingly, the objectives of this research were i) to identify Trichoderma spp. from the Okanagan Valley in British Columbia (BC) by multi-locus gene sequencing and ii) to screen for isolates that can be used as BCA against Diplodia seriata and Neofusicoccum parvum, two of the most prevalent GTD fungi found in BC. In total, 29 Trichoderma isolates were obtained from grapevines in BC. Molecular analyses of the internal transcribed spacer region (ITS1-5.8S-ITS2) of the nuclear ribosomal DNA (rDNA) and a partial sequence of the translation elongation factor 1-alpha gene allowed the identification of seven species, including T. asperelloides, T. atroviride, T. canadense, T. harzianum, T. koningii, T. tomentosum, and T. viticola. Among these, T. canadense and T. viticola are novel species to the scientific community. The antagonistic abilities of Trichoderma species against D. seriata and N. parvum were screened in vitro via dual culture assays and best performing isolates were tested in plantae under greenhouse controlled conditions via detached cane assays alongside commercial pruning wound protectants. The species that performed best under greenhouse conditions were selected to further testing under field conditions in a Merlot vineyard. Trichoderma-based treatments from BC provided >90% reduction of infection when pruning wounds where challenged with the pathogens 1d, 7d, 21d, and 60d post-treatment in the field. Overall, Trichoderma isolates from BC performed similar or better when compared against commercial products. This research represents the initial steps required for the development and registration of local BCA for management of GTD in Canada.Science, Irving K. Barber Faculty of (Okanagan)Biology, Department of (Okanagan)Graduat