Grapevine Pathogenic Microorganisms: Understanding Infection Strategies and Host Response Scenarios

Abstract

Grapevine (Vitis vinifera L.) is one of the most important fruit crop worldwide. Commercial cultivars are greatly affected by a large number of pathogenic microorganisms that cause diseases during pre- and/or post-harvest periods, affecting production, processing and export, along with fruit quality. Among the potential threats, we can find bacteria, fungi, oomycete, or viruses with different life cycles, infection mechanisms and evasion strategies. While plant-pathogen interactions are cycles of resistance and susceptibility, resistance traits from natural resources are selected and may be used for breeding purposes and for a sustainable agriculture. In this context, here we summarize some of the most important diseases affecting V. vinifera together with their causal agents. The aim of this work is to bring a comprehensive review of the infection strategies deployed by significant types of pathogens while understanding the host response in both resistance and susceptibility scenarios. New approaches being used to uncover grapevine status during biotic stresses and scientific-based procedures needed to control plant diseases and crop protection are also addressed.

Keywords: grapevine; host response; infection strategy; pathogenic microorganisms; resistance and susceptibility.

FIGURE 1

Infection strategy of main grapevine pathogenic microorganisms and disease-associated symptoms. Grapevine is affected by different types of microorganisms, i.e., bacteria, fungi, oomycetes and viruses. Agrobacterium vitis causes the grapevine crown gall through the injection of T-DNA sequences via a type-IV secretion system (T4SS), incorporating them in the host genome to induce the synthesis of cytokinins (CK), auxins (AUX) and opines (OP). Xylella fastidiosa is transmitted by insect vectors; it grows and accumulates within the xylem (Xy) vessels causing Pierce’s Disease. Plasmopara viticola zoospores (Z) infect through the stoma in order to accommodate on the host, generating the sporangium (Sp) and generating the grapevine downy mildew (DM) disease. On the other hand, conidia (C) of E. necator, the causal agent of the powdery mildew (PM), infects epidermal layers. However, both P. viticola and E. necator establish their biotrophy by developing haustoria (H) and secreting virulence factors or effectors (Ef) into the host, to manipulate metabolism and defense responses. Botritys cinerea conidia (C) germinate and penetrate the plant tissue by necrotizing the host tissue (mainly in grape berries) through the secretion of cell wall degrading enzymes (CWDE), causing the gray mold disease. Viruses are phloem-limited (Phl) microorganisms, whose infections can cause different symptoms in the host. Ap, appresorium; C, conidium; Cp, conidiophore. Cps, capside.