Abstract

Downy mildew, powdery mildew, and grey mold are some of the phytopathological diseases causing economic losses in agricultural crops, including grapevine, worldwide. In the current scenario of increasing global warming, in which the massive use of agrochemicals should be limited, the management of fungal disease has become a challenge. The knowledge acquired on candidate resistant (R) genes having an active role in plant defense mechanisms has allowed numerous breeding programs to integrate these traits into selected cultivars, even though with some limits in the conservation of the proper qualitative characteristics of the original clones. Given their gene-specific mode of action, biotechnological techniques come to the aid of breeders, allowing them to generate simple and fast modifications in the host, without introducing other undesired genes. The availability of efficient gene transfer procedures in grapevine genotypes provide valid tools that support the application of new breeding techniques (NBTs). The expertise built up over the years has allowed the optimization of these techniques to overexpress genes that directly or indirectly limit fungal and oomycetes pathogens growth or silence plant susceptibility genes. Furthermore, the downregulation of pathogen genes which act as virulence effectors by exploiting the RNA interference mechanism, represents another biotechnological tool that increases plant defense. In this review, we summarize the most recent biotechnological strategies optimized and applied on Vitis species, aimed at reducing their susceptibility to the most harmful fungal and oomycetes diseases. The best strategy for combating pathogenic organisms is to exploit a holistic approach that fully integrates all these available tools.

Highlights

  • Grapevine is one of the world’s most commonly produced fruit crops, with a yield of about 79 million tons of grapes produced only in 2018 (Faostat Database, 2018)

  • It is possible to stimulate host defense biosynthetic pathways [17]. In addition to these biotechnological strategies, new breeding techniques (NBTs) such as genome editing mediated by Clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated 9 (Cas9) technology, a high precision tool capable of strategically introducing targeted mutations in the host genome [18], or cisgenesis/intragenesis which allow the inclusion of gene sequences from sexually compatible plants [19], have been developed and optimized during recent decades

  • Dhekney and colleagues obtained two cisgenic grapevine lines showing broad-spectrum antifungal resistance, by expressing a gene construct codifying for the Vitis vinifera thaumatin-like protein 1 (VVTL-1), that conferred a 10 day delay in symptoms manifestation, compared to the non-transformed control after powdery mildew infection, and a significant resistance to black rot, a fungal disease caused by Guignardia bidwellii [36]

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Summary

Introduction

Grapevine is one of the world’s most commonly produced fruit crops, with a yield of about 79 million tons of grapes produced only in 2018 (Faostat Database, 2018). Sativa, whereas other species are exploited as rootstocks [1], or are used in breeding programs solely for introducing new important traits in selected cultivars [2] This kind of application is somewhat controversial due to international rules, in Europe, where a limitation is imposed on the use of cultivars derived only from Vitis vinifera within breeding programs [3]. It is possible to stimulate host defense biosynthetic pathways (e.g., through the overexpression of transcription factors that enhance the plant defense-related genes) [17] In addition to these biotechnological strategies, new breeding techniques (NBTs) such as genome editing mediated by CRISPR/Cas technology, a high precision tool capable of strategically introducing targeted mutations in the host genome [18], or cisgenesis/intragenesis which allow the inclusion of gene sequences from sexually compatible plants [19], have been developed and optimized during recent decades. This literature review aims to provide an overview of target genes discovered in Vitis species and assessed through the abovementioned biotechnological strategies to increase tolerance to the most severe pathogens, such as grey mold, powdery and downy mildews

Plant Response Mechanisms to Pathogenic Attacks
Overexpression of Pathogenesis-Related Proteins
Gene Expression of Antimicrobial Peptides
Overexpression of Transcriptional Factors
Overexpression of Secondary Metabolites Generally Induced by Biotic Stress
Overexpression or Gene Expression of Other Defense-Related Genes
RNAi: Host- or Spray-Induced Gene Silencing against Fungi and Oomycetes
Genome Editing
Findings
Conclusions
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