Investigations into Physiological, Biochemical, and Histological Modifications in a Vine Decline Associated with Biotic and Abiotic Factors

Abstract

Tunisian table grape production has significantly increased since two decades due to vineyards regional expansion and yield improvement. But, since several years, decline symptoms on Vitis vinifera have been recorded in some areas. A study case of a vineyard in Naassen area (near to Tunis) was chosen to investigate the disease origin and the physiological, biochemical, and histological modifications associated with vine decline. The investigation revealed characteristic symptoms on leaves, old and young shoots similar to decline symptoms of Grapevine Trunk Diseases. Based on cultural characteristics, laboratory investigations revealed the presence of Phaeomoniella chlamydospora and Phaeoacremonium spp., Diplodia seriata and Botryosphaeria dothidea, from root and shoot samples, respectively. These fungi are known as the main pathogens responsible for the Esca, Black dead arm and Excoriose. Molecular analysis confirmed the identification of Diplodia seriata. Beside morphological alterations on leaves and shoots, symptomatic vines presented significant reductions of 30 and 20% in trunk diameter and bud break rate, respectively, and delayed spring growth compared to healthy ones. Furthermore, roots and stems from declined vines contained 3 times more starch than those from asymptomatic ones. Decline survey revealed a heterogeneous dispersion of symptoms in the vineyard in accordance with water supply. The vines along the edge of vineyards are usually less watered and show more decline symptoms. Decline dynamics in time and space scales have to be considered in order to develop effective management strategies