Project Number
US PP LM 16-04

Project title
Investigation into the Efficacy of Trichoderma spp. Colonization of Grapevine Nursery Plants.

Project leader
Mostert, M

Institution
University of Stellenbosch. Faculty of AgriSciences. Department of Plant Pathology

Team members
Mostert, L
Halleen, F
Pierron, R

Completion date
2019

Project description
Trichoderma spp. has the potential to prevent infection of black foot disease (BFD) pathogens of nursery vines. The objectives included i) testing the efficacy of Trichoderma spp. against black foot pathogens in vitro; testing different Trichoderma products and methods of application; determine the extent of Trichoderma colonisation of rootstocks and roots and lastly, to assess the activation of grapevine rootstock defence genes by Trichoderma spp.
Ten Trichoderma spp. isolates were tested in vitro for their ability to inhibit the mycelial growth of four BFD pathogens by means of volatile organic compounds (VOCs), diffusible antibiotic compounds (DACs) and direct antagonism. Field trials were conducted over two seasons to assess i) the effect of different application methods and ii) different commercially available Trichoderma products on Trichoderma colonization and BFD control. Trichoderma colonization of dormant rootstock shoots were assessed by soaking the shoots in spore suspensions. Additionally, early Trichoderma colonization was investigated by drenching young rooted rootstock plants with spore suspensions. Infection and growth was further observed by generating a fluorescent T. atroviride T77:tdTomato strain through Agrobacterium transformation. The activation of defence genes of rooted rootstock plants were assessed after 10 and 21 days of drenching with Trichoderma suspensions. mRNA was extracted from leaves and the expression levels of twelve defence genes in relation to two housekeeping genes determined.
In most cases Trichoderma inhibited the growth of BFD pathogens, though higher growth inhibition was obtained with the DACs than the VOCs. For both classes of compounds D. macrodidyma were found to be more sensitive. From the field trials’ testing, the different application methods clearly showed that dipping the basal ends in a dry formulation followed by monthly soil drenches, consistently gave higher colonization of Trichoderma spp. Field drenching alone was significantly less effective. Soaking of the basal ends of vines in a conidial suspension for one hour was  ineffective and did not differ from the untreated control. The trial evaluating different Trichoderma-based products showed products that contain T. atroviride originating from grapevine, namely Eco 77®, USPP-T1 and USPP-MT1 to be more effective in colonizing nursery vine rootstocks. In the 2016/17 season all of the products resulted in significantly lower BFD pathogen incidence in the basal ends of the vines. Trichoderma atroviride has the ability to colonise grapevine roots as well as the base of the rootstock of young plants three days post drenching. The early establishment of T. viride T77: tdTomato could be visualised within roots after 21 days with confocal microscopy. On dormant rootstock shoots did a longer soaking period not significantly increase T. atroviride colonization. The gene expression results showed that the cultivar, Trichoderma isolate and time assessed had an effect on defence gene induction.
The newly developed application technique consisting of a dry product application to the basal ends of vines post callusing in combination with monthly soil drenches gave consistent better colonization of Trichoderma spp. over the two seasons, while simultaneously providing a certain degree of protection against infection of the basal ends of vines to BFD pathogens. This protection was, however, not found on the roots, most probably due to the larger volume of roots exposed to black foot inoculum in the soil.
Black foot infections of nursery vines can’t solely be controlled by Trichoderma applications and need to be incorporated in an integrated control strategy. To ensure black foot free nursery vines, the best method of control would be hot water treatment of vines prior to sale.

Presentation(s)
Van Jaarveld, W, Halleen, F and Mostert, L. 2016. Investigation into the efficacy of Trichoderma spp. colonization of grapevine nursery plants for improved black foot control. Lecture. Friday Forum, University of Stellenbosch, Faculty of AgriScience, Department Plant Pathology. 1 April, Stellenbosch, South Africa.

Van Jaarsveld, W, Halleen, F and Mostert, L. 2016. In vitro screening of Trichoderma species isolates for potential bio-control of black foot disease causing pathogens in grapevine nurseries. Paper presented at the 14th Meeting of Working Group Biological Control of Fungal and Bacterial Plant Pathogens (IOBC), 12-15 September, Berlin, Germany.

Van Jaarsveld, W J, Mostert, L and Halleen, F. 2017. In vitro screening of Trichoderma species isolates for potential bio-control of black foot disease-causing pathogens in grapevine nurseries. Paper presented at the Congress of the South African Society of Plant Pathology, 15-19 January, Drakensberg, South Africa.

Van Jaarsveld, W J, Halleen F and Mostert, L. 2017. The evaluation of the extent of Trichoderma colonization of dormant rootstock vines. Paper presented at the Plant Bioprotech: 1st International Symposium on Plant Bioprotection Sciences and Technologies, 27-30 June 2017, Reims, France.

Van Jaarsveld WJ, Halleen F, Mostert. 2018. The effect of different application methods on the colonization of Trichoderma atroviride of grapevine nursery vines post callusing. SASEV-WINETECH 41st International Conference (2-4 October 2018, Somerset West).

Pierron R, Stempien E, Adendendorf I, Halleen F, Mostert L. 2018. Investigating the early colonization and host defence activation of the biological control agent Trichoderma atroviride in the grapevine rootstock Richter 110. SASEV-WINETECH 41st International Conference (2-4 October 2018, Somerset West).

Stempien E, Pierron R, Adendendorf I, Halleen F, Mostert L. 2019. Root colonization and host defence activation of grapevine rootstock by the biological control agent Trichoderma atroviride. 51st Congress of the South African Society of Plant Pathology, South Africa (20-24 January 2019, Langebaan). Received prize for best oral biocontrol presentation.

Van Jaarsveld WJ, Halleen F, Mostert L. 2019. Investigating the colonization of Trichoderma in grapevine nursery vines for improved management of black foot disease. 51st Congress of the South African Society of Plant Pathology, South Africa (20-24 January 2019, Langebaan).

Van Jaarsveld W, Stempien E, Pierron R, Halleen F, Mostert L. An overview of lessons learnt in the application of Trichoderma products in grapevine nurseries. 11th International Workshop on Grapevine Trunk Diseases, 7-12 July 2019, Penticton, British Columbia, Canada.

Stempien E, Pierron R, Addendorf I, Halleen F, Mostert L. 2019. Root colonization and host defence activation of grapevine rootstock by the biocontrol agent Trichoderma atroviride. 11th International Workshop on Grapevine Trunk Diseases, 7-12 July 2019, Penticton, British Columbia, Canada.

Publications

Van Jaarsveld WJ. 2019. Investigation of Trichoderma species colonization of nursery grapevines for improved management of black foot disease. MSc Thesis. Stellenbosch University.

Van Jaarsveld WJ, Mostert L, Halleen F. 2019. Investigation of Trichoderma species colonization of nursery grapevines for improved management of black foot disease. Article in preparation.

Stempien E, Pierron R, Adendendorf I, Halleen F, Mostert L. 2019. Root colonization and host defence activation of grapevine rootstock by the biological control agent Trichoderma atroviride. Article in preparation.