Physiological and Molecular Responses of Vitis vinifera cv. Tempranillo Affected by Esca Disease

Abstract

Esca is a multi-fungal disease affecting grapevines. The objective of the study was to evaluate the physiological and molecular response of the grapevine cv. Tempranillo to esca disease, carried out in a vineyard under Mediterranean climatic conditions in western Spain. The photosynthetic pigments in the leaves decreased, with a strong decrease in the photosynthetic efficiency. The proline content increased significantly in the early stages of affected leaves, being possibly involved in the maintenance of lipid peroxidation levels in leaves, which do not increase. The phenol, flavonoid, and phenylpropanoid content decreased in esca-affected leaves, as does the total antioxidant capacity (FRAP), while the polyphenol oxidase (PPO) activity suffers a strong increase with the development of the disease. In affected grapes, the lipid peroxidation and the total phenol content decrease, but not the anthocyanin content. The ascorbate pool decreases with the disease and with time. On the other hand, pool GSH + GSSG is lower in affected leaves, but increases with time. These alterations show a clear change in the redox homeostasis. The expression of genes phenylalanine ammonia lyase (PAL), polyphenol oxidase (PPO), superoxide dismutase (SOD), and chalcone synthase (ChaS1 and ChaS3) become considerably higher in response to esca, being even higher when the infection time increases. The alteration of AsA and GSH levels, phenolic compounds, PPO activity, proline content, and FRAP, together with the increase of the PAL, PPO, SOD,ChaS1, and ChaS3 gene expression, are clearly implicated in the esca response in plants. The expression of these genes, similar to the PPO activity, can be used as markers of state in the development of the disease.

The Use of Mannans as a Sustainable Approach to Activate Vitis vinifera Innate Immunity in Response to Fungi Causing Grapevine Trunk Diseases (GTD)

“…Those authors report no differences in the chlorophyll a/b ratio between healthy and diseased leaves, apparently because the two chlorophylls are damaged in the same way. García et al [23] describe similar results for cv. Tempranillo, with a decrease in chlorophyll content in vines affected by tinder, and no variation due to the effect of tinder in the carotenoids in the vines harvested in August but an increased carotenoid/chlorophyll ratio.…”

“…Decreased phenol content due to the effect of tinder has already been described by other workers [23,75]. This could be due to the involvement of phenols in defence reactions, being derived for the synthesis of compounds such as lignin [76].…”

“…Cabernet Sauvignon grapes from vines affected by tinder. García et al [23], however, indicate that tinder does not affect the anthocyanin content in cv. Tempranillo grapes, which results that coincide with those of the present work in DT0.…”

“…Santos et al [70] also observed decreased chlorophyll a and b contents in infected vines, with an increased chlorophyll a/b ratio, the behaviour depending on the variety studied. García et al [23] observed a decrease in both chlorophylls in cv. Tempranillo affected by tinder, with increases in the chlorophyll a/b and the carotenoid/chlorophyll ratios despite the lower carotenoid content.…”

“…When this type of fungus colonizes this tissue, it causes deterioration of the host plant due to the loss of xylem function and the consequent decrease in hydraulic conductivity [18][19][20]. Moreover, pathogenic fungi can produce compounds that activate secondary metabolism, increasing anthocyanin synthesis and key enzymatic reactions (NADPH oxidase and phenylalanine ammonia lyase) or oxidative enzymes such as laccases (a type of PPO) leading to the oxidation of phenols and polyphenols [21][22][23]. New fungal species with this pathogenic capacity continue to be discovered.…”