The Guignardia project

Monitoring and molecular characterization of Guignardia bidwellii, agent of the Black Rot of grape

Barbara Wicht, Agroscope, Cadenazzo/ETH-Zürich
Mauro Jermini (Agroscope, Cadenazzo), Cesare Gessler, Giovanni Broggini (Plant Pathology, Swiss Federal Institute of Technology, Zurich), Orlando Petrini (Istituto cantonale di microbiologia, Bellinzona)

The Guignardia project

The ascomycete Guignardia bidwellii is the agent of the Black Rot of grape, a disease that can cause reduced plant health and heavy crop losses in vineyards. Black Rot is native to North America and was introduced in Europe in the 19th century. Nowadays, it regularly occurs in France, Italy, Germany and southern Switzerland (Canton Ticino).

Aim of our study is to investigate the genetic variability of G. bidwellii. The comparison of strains originated from different countries will allow to understand the dynamic of the introduction of Black Rot in Switzerland and other regions, the modality of its diffusion (i.e. when and how infections occur), how fast and far its spreads, and to study its sexuality (homo- vs. heterotallism). Such knowledge will improve the control of this disease, and finally estimate the risk of developing resistance against some type of fungicides.

Background
Molecular tools are of key importance in the monitoring and epidemiology of pathogens. Nevertheless, very few studies have been carried out worldwide to investigate the genetic structure of G. bidwellii. A first study based on microsatellite fingerprinting was carried out at the Swiss Federal Institute of Technology (Zurich) by Angst (2007). The results showed that 93% of the mummified berries were infected by a single genotype, bringing into question the importance of infection caused by sexual stages. Alternatively considering its sexuality, the fungus could have a homothallic behavior. Moreover, the genetic diversity was smaller in the population originated from Canton Ticino (Cadenazzo), where only 3 genotypes were present (one highly predominant) possibly indicating a relevant bottleneck at its introduction into Ticino. Conversely, in France, 12 genotypes could be identified. It is not clear yet whether these results depend on the number and the polymorphic degree of the microsatellites developed for the molecular fingerprinting, or if the genetic variability observed at the leaf level corresponds to a restricted number of genotypes able to attack the berries.

Your contribution

If you wish to contribute to this research project by sending us your samples of Grape tissues (berries and leaves) download the pdf file describing how to proceed to announce for the collaboration and for the sampling strategy. Your collaboration will be acknowledged.

Barbara Wicht, PhD
Agroscope Changins-Wädenswil ACW
Forschungszentrum Cadenazzo
CH-6594 Contone