Epidemiology of Petri disease pathogens: Inoculum sources and vine to vine spread of the disease within vineyards

Project Number
WW 06-41

Project title
Epidemiology of Petri disease pathogens: Inoculum sources and vine to vine spread of the disease within vineyards

Project leader
Halleen, F

Team members
Halleen, F
Mostert, L
Shubane, A
Vermeulen, C
Marais, J

Completion date
2016

Project description
The aim of this study was to identify fruiting bodies of Petri disease in local vineyards, to study spore release patterns and to determine their role as inoculum sources. Although Petri disease has been studied for more than 20 years locally, little attention has been given to the spread of the disease within vineyards, and no study has investigated the actual source of pathogen inoculum, the fruiting bodies that produce and release the spores in local vineyards. Phaeomoniella chlamydospora is known to produce fruiting structures (pycnidia) which have only been found in Australian vineyards. Fruiting bodies (perithecia) of only two of the 22 Phaeoacremonium species associated with grapevines worldwide, Pm. minimum and P. mortoniae, respectively, have thus far been found on grapevines in California.
Selected wood pieces were investigated under a microscope for fruiting bodies. Spore trapping studies were conducted in 6 vineyards and 2 rootstock mother blocks over two seasons. Mating studies were conducted with selected Phaeoacremonium spp. in vitro to induce fruiting structures. Infection studies were conducted with Phaeomoniella chlamydospora spores obtained from pycnidia. Pathogenicity studies with newly found Phaeoacremonium spp. or species which have not been subjected to pathogenicity studies in local vineyards were conducted on field-grown vines by inoculating grapevine pruning wounds. A population genetics study was conducted with selected Pm. minimum isolates to get a better understanding of the origin of inoculum in Western Cape vineyards.
During the study Pm. minimum perithecia and Pa chlamydospora pycnidia were found in several vineyards as well as rootstock mother blocks, no other perithecia could be found which raises the question where these inoculum comes from. In vitro mating studies with Pm. scolyti and Pm. australiense isolates produced perithecia which were used to describe these sexual morphs. Spore trapping studies were conducted in six vineyards and two rootstock mother blocks from mid-March to the beginning of December 2012 and 2013. Pa. chlamydospora and 14 Phaeoacremonium species were detected in these vineyards.
The studies also clearly showed that inoculum is available during traditional pruning and de-suckering periods. No correlation could be found between spore release and specific weather conditions (i.e. rainfall), and therefore farmers must be aware that spores are also released during dry periods. Pruning wound protection is therefore the only solution to prevent these infections. A pathogenicity trial conducted with nine Phaeoacremonium species found in South African vineyards for the first time on Cabernet Sauvignon pruning wounds indicated that all the Phaeoacremonium species were pathogenic. A population genetic study was also conducted with 320 Pm. minimum isolates. Preliminary analyses indicate that sexual as well as asexual reproduction occurs within vineyards. Pm. minimum perithecia and Pa chlamydospora pycnidia were found in several vineyards as well as rootstock mother blocks. Spore trapping studies showed that spores are released throughout the year. The study concluded that asexual reproduction plays a major role and that infected propagation material is a major mode of disease spread. Asexual and sexual reproduction occurs in vineyards. Pruning wound protection in rootstock mother blocks and sanitation practices during the propagation process is therefore highly recommended, together with pruning wound protection strategies and sanitation practices in established vineyards to combat Petri disease.

Poster(s)
Baloyi, A, Mostert, L, Eskalen, A and Halleen, F. 2013. Occurrence of Togninia minima in South African vineyards. Poster presented at the 48th Congress of the Southern African Society for Plant Pathology. 20-23 January, Warmbaths, South Africa.

Baloyi, M A, Mostert, L and Halleen, F. 2015. Spore release patterns of Petri disease pathogens, Phaeomoniella clamydospora and Phaeoacremonium spp. in South African vineyards. Poster presented at the 49th Congress of the Southern African Society for Plant Pathology. 19-21 January 2015, Bloemfontein, South Africa.

Baloyi, M A, Mostert, L, Halleen, F. 2016. Pathogenicity of Phaeoacremonium species recently found in Western Cape vineyards. Poster presented at the 38th South African Society for Enology and Viticulture Conference. 23-25 August, Somerset, South Africa.

Presentation(s)
Halleen, F. 2012. THRIP Audit: Epidemiology and etiology of Esca on grapevine in South Africa. Presentation at ARC Infruitec-Nietvoorbi,j 28 August, Stellenbosch, South Africa.

Baloyi, M A, Halleen, F and Mostert, L. 2012. Inoculum ecology of Petri disease fungi of grapevines in South Africa. Lecture. The University of Stellenbosch. Faculty AgriSciences. Department of Plant Pathology. 9 November, Stellenbosch, South Africa.

Baloyi, M A, Halleen, F and Mostert, L. 2013. Spore release of Petri disease pathogens in vineyards. Lecture. University of Stellenbosch. Faculty AgriSciences. Department of Plant Pathology. 10 May, Stellenbosch, South Africa.

Halleen, F. 2013. Grapevine trunk diseases: A South African perspective. Lecture. Instituto Federal, Rio. 28 October 2013, Grande do Sul, Brazil.

Baloyi, M A, Mostert, L and Halleen, F. 2013. Epidemiology of Petri disease pathogens: Inoculum sources and vine to vine spread of the disease within vineyards. Paper presented at the 35th South African Society for Enology and Viticulture Conference. 13-15 November, Somerset West, South Africa.

Baloyi, M A, Mostert, L and Halleen, F. 2014. Inoculum ecology of Petri disease pathogens: In-depth investigation in one vineyard in Rawsonville. Lecture. University of Stellenbosch, Faculty AgriSciences, Department of Plant Pathology. 4 April 2014, Stellenbosch, South Africa.

Baloyi, M A, Mostert, L and Halleen, F. 2014. Mating results of Phaeoacremonium scolyti with the first report of the sexual stage. Lecture. University of Stellenbosch, Faculty AgriSciences, Department of Plant Pathology. 31 October 2014, Stellenbosch, South Africa.

Baloyi, M A, Mostert, L and Halleen, F. 2014. Spore release patterns of Petri disease fungi in South African vineyards and rootstock mother blocks. Paper presented at the 9th International Workshop on Grapevine Trunk Diseases. 18-20 November 2014, Adelaide, Australia.

Halleen, F and Mostert, L. 2015. Grapevine trunk diseases: A South African experience. Lecture. INRA. 18 June 2015, Bordeaux, France.

Halleen, F and Mostert, L. 2015. Management of grapevine trunk diseases through pruning wound protection. Paper presented at the International Seminar Control Strategies of Grapevine Trunk Diseases. 23 April 2015, Santiago, Chile.

Halleen, F and Mostert, L. 2015. South African perspective of grapevine trunk diseases: Biocontrol and future perspectives. Paper presented at the International Seminar Control Strategies of Grapevine Trunk Diseases. 22 April 2015, Santiago, Chile.

Halleen, F and Mostert, L. 2015. Grapevine trunk disease research in South Africa. Presentation at the Workshop: COST Action FA 1303: Sustainable control of GTDs: current state and future prospects. 23-24 June 2015, Cognac, France.

Baloyi, MA, Mostert, L, Halleen, F. (2015). Inoculum ecology of Phaeomoniella chlamydospora. Lecture. University of Stellenbosch. Faculty AgriSciences, Department of Plant Pathology. 4 September, Stellelnbosch, South Africa.

Baloyi, M A, Mostert, L, Halleen, F. 2016. Inoculum sources and spore release patterns of Petri disease pathogens in Western Cape vineyards. Presentation at the 38th South African Society for Enology and Viticulture Conference. 23-25 August, Somerset, South Africa.

Halleen, F, Mostert, L. 2016. What can be done to prevent/manage trunk diseases, and should we treat pruning wounds. Presentation at VinPro Information Day. 4 May, Malmesbury, South Africa.

Halleen, F, Mostert, L. 2016. What can be done to prevent/manage trunk diseases, and should we treat pruning wounds. Presentation at VinPro Information Day. 19 May, Stellenbosch, South Africa.

Baloyi, M A, Mostert, L, Halleen, F. 2016. Survey of Phaeoacremonium minimum fruiting bodies and mating type distribution in vineyards. Lecture. University of Stellenbosch, Faculty AgriSciences, Department of Plant Pathology. 22 April, Stellenbosch, South Africa.

Spies, CFJ, Moyo, P, Mostert, L, Halleen, F. (2017). Phaeoacremonium species diversity and hostrange in the Western Cape Province of South Africa. Presentation at the 10th International Workshop on Grapevine Trunk Diseases (4-7 July, Reims, France)

Halleen, F, Mostert, L. (2017). Advances made in grapevine trunk disease research. INVITED LECTURE at 40th SASEV Conference (29-31 August 2017, Simondium)

Articles
Baloyi, A, Halleen, F, Mostert, L. 2013. First report of Togninia minima perithecia on esca- and petri-diseased grapevines in South Africa, Plant Disease, Mnth Sep v. 97 (9) (p. 1247)
dx.doi.org/10.1094/PDIS-10-12-0963-PDN

Baloyi, M A, Halleen, F, Mostert, L, Eskalen, A. 2016. First report of Phaeomoniella chlamydospora Pycnidia as Petri disease inoculum sources in South African vineyards, Plant Disease, Mnth 15 Sep v. 97 (9) (p. 1247)
http://dx.doi.org/10.1094/PDIS-04-16-0569-PDN

 

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