Studies on black leaf symptom development and its impact on nutrient profile and fruitfulness in Thompson Seedless grapevines grafted on Dogridge rootstock

Salinity issues in the Indian vineyards have led to a number of nutritional imbalances leading to the decline in productivity of grapes. Black leaf is one such disorder which is adversely affecting the vineyards productivity. The vines having black leaf symptoms had significantly lesser number of fruitful canes than healthy ones. The symptom development reduced the bunch weight significantly. Chlorophyll content was significantly lower in the symptomatic leaves. The leaf analysis of symptomatic vines revealed significantly lower K, i.e. 0.35% in petiole and 0.31% in leaf blade compared to 1.39% K in petioles and 0.59% in leaf blade in healthy vines. However, the leaf blades analysis of symptomatic vines revealed significantly higher Na (1.10%) compared to 0.46% in healthy vines. Lower K and higher Na content and narrow K:Na ratio was found to be associated with the symptom development. Phosphorus content was significantly reduced in the affected tissues. Chloride content in the tissue was not high enough to cause leaf blackening and necrosis. The micronutrients Zn, Fe, Cu and Mn were also not found associated with the development of symptom. High content of Na in vine tissues (>1.0%) grafted on Dogridge rootstock suggests that this rootstock could not exclude Na under saline irrigation.