Canadian Forest Service Publications

Trichoderma spp.: antagonistic effects to Phytophthora ramorum growth and spore germination in vitro. 2011. Becker, E.M.; Rajakulendran, N.; Shamoun, S.F. Pages 173-174 in Plant Canada Conference Proceedings, July 17-21, 2011, Halifix, Nova Scotia. Plant Canada.

Year: 2011

Available from: Pacific Forestry Centre

Catalog ID: 32644

Language: English

CFS Availability: PDF (download)

Abstract

The pathogen Phytophthora ramorum (Werres, De Cock & Man in't Veld), is responsible for Sudden Oak Death in California and Oregon and Sudden Larch Death in the UK, and causes foliar blight symptoms in many host plant species. In British Columbia, several nurseries have reported P. ramorum-infected plants, and eradication measures have been taken to prevent the spread of the pathogen beyond these points of entry and limit this potential pathway for escape into forested or wild areas. We are investigating the potential use of Trichoderma spp. to limit infection of plants and reduce the spread of P. ramorum. About 50 isolates of Trichoderma of eight species were assayed. Direct contact antagonism of P. ramorum was evaluated using a dual174 culture assay in Petri plates, which measured the ability of Trichoderma isolates to overgrow and kill cultures of P. ramorum. In dual culture, the species with the fastest rates of overgrowth were T. atroviride, T. koningii and T. virens (9.0, 7.8, and 6.9mm/day), which also had the fastest rates of lethal effect on P. ramorum (9.0, 6.1, and 5.5mm/day). A high rate of overgrowth did not always translate to a lethal effect on P. ramorum. These results suggest that certain species of Trichoderma have the ability to kill P. ramorum after it has established. The effects of Trichoderma metabolites on P. ramorum (antibiosis) were investigated using a microplate assay. Zoospores of P. ramorum were added to media containing cell-free Trichoderma culture extracts, and germination and growth were evaluated over several days. The species that produced the most inhibitory extracts in microplate assays were T. polysporum, T. pseudokonigii, and T. harzianum (99, 73 and 68% inhibition). Trichoderma isolates were also tested for their ability to tolerate chemical controls that are registered for use in Canada by measuring their growth on media containing either fosetyl-Al (AlietteTM) or metalaxyl (Subdue MaxxTM). All isolates were inhibited by Aliette, but many isolates were tolerant of Subdue Maxx. This allows for the possibility of combining or alternating promising Trichoderma isolates with Subdue Maxx in an integrated pest management approach.

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