Effects of Grapevine red blotch-associated virus on vine physiology and fruit composition of field grown grapevine cv. Gamay
Jean-Sébastien Reynard and Paul Gugerli Agroscope, CP 1012, 1260 Nyon, Switzerland jean-sebastien.reynard@agroscope.admin.ch
Grapevine red blotch-associated virus (GRBaV) is a recently discovered viral pathogen. This circular DNA virus has been shown to be associated with red blotch disease. In this study, we evaluated the impact of GRBaV infection on grapevine physiology and fruit composition of field-grown cv. Gamay under cool-climate conditions of Switzerland. Preliminary results presented here showed a clear negative effect on GRBaV infection on vine physiology and fruit composition at harvest. Therefore, testing for this pathogen should be included in certification programs.
Introduction
Grapevine red blotch-associated virus (GRBaV) is a recently discovered viral pathogen (Krenz et al., 2012).
This circular DNA virus has been shown to be associated with red blotch disease (Al Rwahnih et al., 2013).
The main symptom of the disease on red cultivars is reddening of leaf blade. This reddening can be confused with symptoms of grapevine leafroll disease. Poojari et al. (2013) have shown that GRBaV infection can be detrimental to the quality of harvest. In this study, we evaluated the impact of GRBaV infection on grapevine
physiology and fruit composition of field grown cv. Gamay under cool-climate conditions of Switzerland.
Materials and Methods
Two accessions in our grapevine virus collection, Zinfandel (A2V13) and Emperor (A2V18), were found to be infected with GRBaV by PCR using primers developed by Krenz et al. (2014). These two accessions were introduced into our collection in 1985 from UC Davis (California). The Zinfandel accession was tested for the presence of others viruses and appeared only infected by GRBaV. GRBaV from Zinfandel accession was graft-inoculated onto the leafroll indicator Vitis vinifera cv. Gamay Rouge de la Loire rooted on 3309 Couderc.
Two block of three plants were planted at the Agroscope research station in Nyon in 2000. Fruit composition at harvest and physiological parameters were determined for the 2014 season. Leaf chlorophyll
concentrations were estimated using an N-tester chlorophyll meter (Yara, France). Net photosynthesis (Pn), stomatal conductance (gs) and transpiration (E) were determined on two adult leaves per plant at two time points using the LICOR 6400 XT portable photosynthesis system (Nebraska, USA). Fruit parameters at harvest were measured by NIR spectroscopy (WineScanTM,FOSS, US) at Agroscope oenological laboratory.
Results and Discussions
Under cool-climate condition of Switzerland, first symptoms on Gamay leaves appeared during summer. We selected therefore two periods for studying photosynthesis: 18 July (asymptomatic stage) and 8 September (symptomatic stage). The photosynthesis parameters were already impacted in mid-July before development of symptoms. Photosynthesis and transpiration were reduced by around 30% in GRBaV infected vines compared to controls (Table 1). Measurement of photosynthesis during symptomatic stage showed a similar effect.
Table 1. Effects of GRBaV infection on photosynthetic parameters measured on two time points: net
photosynthesis (Pn, µmol CO2 m-2 s-1), stomatal conductance (gs,(mol CO2 m-2 s-1) and transpiration (E, mmol H2O m-2 s-1 ). Means with *, **, *** are significantly different at P ≤ 0.05, respectively P ≤ 0.01 and P ≤ 0.001.
18.7.2014 8.9.2014
Pn gs E Pn gs E
Healthy
control 16.7*** 0.25*** 5.0* 14.8*** 0.23* 4.3*
GRBaV
infected 12.1*** 0.14*** 3.30* 11.1*** 0.15* 3.3*
Leaf chlorophyll content was monitored repeatedly during the growing season (Fig. 1). GRBaV-infected vines showed consistently reduced leaf chlorophyll content.
Figure 1. Leaf chlorophyll content in GRBaV-infected and healthy vines at different period during the 2014 season. Each point represents a mean with its 95% confidence intervals. * represents time of veraison.
Results of fruit composition at harvest are displayed in Table 2. The infection by GRBaV was associated with modifications of fruit composition. Fruits from grapevines infected by GRBaV showed lower sugar content and higher pH. The berry acid composition was modified by GRBaV infection: lower tartaric acid content but higher malic acid content in berries.
Table 2. Effects of GRBaV infection on Gamay. Fruit composition at harvest, 2014. Means with **, *** are significantly different at P ≤ 0.01, respectively P ≤ 0.001.
Soluble solids contents
(% Brix)
pH
Titratable acidity (g tartrate/L)
Tartaric acid (g/L)
Malic acid (g/L)
Healthy
control 20.5*** 3.0*** 12.9 8.3*** 6.7**
GRBaV
infected 18.1*** 3.2*** 12.8 7.1*** 8.2**
In conclusion, the preliminary results presented here showed a clear negative effect on GRBaV infection on vine physiology and fruit composition at harvest of cv. Gamay under cool-climate conditions of Switzerland.
Therefore, our results confirm studies and observations made previously about the negative effect of GRBaV on grape production. Considering those observations and the harmful effect of GRBaV on grapevine, virus monitoring in vineyards should be undertaken in order to verify if GRBaV is restricted only to North America and testing for this pathogen should be included in certification program.
Acknowledgments
Sincerest thanks to Vivian Zufferey for photosynthesis measurement and Fabrice Lorenzini for fruit composition analysis.
References
Al Rwahnih, M., Dave, A., Anderson, M.M., Rowhani, A., Uyemoto, J.K., Sudarshana, M.R., 2013. Association of a DNA Virus with Grapevines Affected by Red Blotch Disease in California. Phytopathology 103, 1069-1076.
Krenz, B., Thompson, J.R., Fuchs, M., Perry, K.L., 2012. Complete Genome Sequence of a New Circular DNA Virus from Grapevine.
Journal of Virology 86, 7715-7715.
Krenz, B., Thompson, J.R., McLane, H.L., Fuchs, M., Perry, K.L., 2014. Grapevine red blotch-associated virus Is Widespread in the United States. Phytopathology 104, 1232-1240.
Poojari, S., Alabi, O.J., Fofanov, V.Y., Naidu, R.A., 2013. A leafhopper-transmissible DNA virus with novel evolutionary lineage in the family geminiviridae implicated in grapevine redleaf disease by next-generation sequencing. Plos One 8, e64194.
