Grapevine leafroll disease alters leaf physiology but has little effect on plant cold hardiness

Abstract

Foliar sugar accumulation in grapevines with leafroll disease was correlated with lower photosynthesis, likely due to feedback inhibition. However, cold acclimation of dormant tissues remained unaffected by the virus status. Grapevine leafroll-associated viruses (GLRaV) contribute to losses in fruit yield and quality worldwide. Visually, leafroll disease symptoms appear similar to those associated with an imbalance in source/sink relations and a concomitant feedback inhibition of photosynthesis, which is often caused by an impasse in sugar translocation. In order to test this potential relationship and related physiological responses, leaf water status, gas exchange, non-structural carbohydrates, and dormant tissue cold hardiness were examined over 2 years in healthy and GLRaV-3-infected, field-grown Merlot grapevines. Diurnal and seasonal changes in leaf water status and gas exchange were dominated by variations in water availability, temperature, and leaf age, while GLRaV-3 infection contributed less to the overall variation. By contrast, foliar carbohydrates increased markedly in infected plants, with starch accumulating early in the growing season, followed by soluble sugar accumulation, leaf reddening, and declining gas exchange. Photosynthesis correlated negatively with leaf sugar content. However, dormant-season cold hardiness of buds and cane vascular tissues was similar in healthy and infected vines. These findings support the idea that visible symptoms of grapevine leafroll disease are a consequence of carbohydrate accumulation which, in turn, may lead to feedback inhibition of photosynthesis. In addition, this study provided evidence that GLRaV-3 infection is unlikely to alter the susceptibility to moderate water deficit and winter damage in mature Merlot grapevines.

Water Deficits Do Not Improve Fruit Quality in Grapevine Red Blotch Virus-Infected Grapevines (Vitis vinifera L.)

“…Decreases in leaf gas exchange in GRBV+ vines have been hypothesized to be a response to an accumulation of leaf carbohydrates that result in feedback inhibition of carbon assimilation (Martıńez-Lüscher et al, 2019). This mechanism would be similar to that which has been recently shown in vines infected with Grapevine leafroll-associated virus, another phloemlimited virus with similar symptomology (Halldorson and Keller, 2018). In general, feedback inhibition of carbon assimilation and synthesis of anthocyanins in leaves in response to foliar sugar accumulation has been well-documented in grapevine (Downton et al, 1987;Roper and Williams, 1989;Quereix et al, 2001;Gutha et al, 2010).…”

“…In general, feedback inhibition of carbon assimilation and synthesis of anthocyanins in leaves in response to foliar sugar accumulation has been well-documented in grapevine (Downton et al, 1987;Roper and Williams, 1989;Quereix et al, 2001;Gutha et al, 2010). Halldorson and Keller (2018) also showed that accumulation of anthocyanins in leaves preceded other signs of senescence. Therefore, it is likely that GRBV effects on leaf carbohydrate metabolism and gas exchange precede the foliar accumulation of anthocyanins, suggesting that these flavonoids act as a photoprotectant of the photosynthetic apparatus that is unable to quench the excess light energy through normal photochemistry (Feild et al, 2001).…”

Characterizing the spatial distributions of spotted lanternfly (Hemiptera: Fulgoridae) in Pennsylvania vineyards

“…This may explain why our study failed to find a significant effect of SLF abundance on the prevalence of dead shoots. Red leaves on red producing cultivars were significantly related with SLF abundance, which could be used as a metric to predict stressed plants and inform potential changes in sap flow and nutrient status of the vine 29 . Crown gall was not significantly related to SLF abundance; however, our study did not include measurements of crown gall in the vineyards prior to SLF infestations, which limits our ability to address this relationship.…”

“…In spring 2019 and 2020, the number of dead shoots, living shoots, and clusters on each shoot were counted on all monitored vines to evaluate the relationship between SLF infestation and bud fruitfulness and survival. Leaf redness in grapevines has been related to reduced translocation and accumulation of sugars within the canopy 29 , which may be linked to phloem feeding by SLF. In the fall of 2019, percent leaf redness was estimated on a scale of 0-100% for www.nature.com/scientificreports/ all monitored vines.…”

Fire Blight Management: Physiological Assessment of Cultural Control By Pruning in Pear Orchards

“…Besides fluorescence parameters, sugars/starch quantifications are robust and simple complementary tools to better discriminate the physiological condition of plants, as sugars are essential for plant development and production, and are involved in crucial signalling and metabolomic processes (e.g., metabolic resource and regulators) (Zhang et al 2017). Leaves infected by pathogens showed inhibition of net carbon assimilation rate, reduced ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO) activity, stomatal conductance, mesophyll conductance, and chlorophyll content (Polanco et al 2014;Halldorson & Keller 2018). These photosynthetic endpoints are thus critical to assess if pruning is being effective -as a cultural control strategy -in maintaining the plant homeostasis and carbohydrates availability for the normal plant development, including fruiting/ripening.…”