Rpv29, Rpv30 and Rpv31: Three Novel Genomic Loci Associated With Resistance to Plasmopara viticola in Vitis vinifera.

Maryam Sargolzaei,Osvaldo Failla,Piero Attilio Bianco,Nana Bitsadze,David Maghradze,Gabriella De Lorenzis,Giuliana Maddalena,Silvia Laura Toffolatti

doi:10.3389/fpls.2020.562432

Abstract

Plasmopara viticola (Berk. et Curt.) Berl. and de Toni, the agent of downy mildew, is one of the most important pathogens of European grapevine (Vitis vinifera L.). Extensive evaluation of cultivated grapevine germplasm has highlighted the existence of resistant phenotypes in the Georgian (Southern Caucasus) germplasm. Resistance is shown as a reduction in disease severity. Unraveling the genetic architecture of grapevine response to P. viticola infection is crucial to develop resistant varieties and reduce the impact of disease management. The aim of this work was to apply a genome-wide association (GWA) approach to a panel of Georgian-derived accessions phenotyped for P. viticola susceptibility and genotyped with Vitis18kSNP chip array. GWA identified three highly significant novel loci on chromosomes 14 (Rpv29), 3 (Rpv30) and 16 (Rpv31) associated with a low level of pathogen sporulation. Rpv29, Rpv30, and Rpv31 loci appeared to be associated with plant defense genes against biotic stresses, such as genes involved in pathogen recognition and signal transduction. This study provides the first evidence of resistant loci against P. viticola in V. vinifera germplasm, and identifies potential target genes for breeding P. viticola resistant grapevine cultivars.

Highlights

Vitis vinifera L. is one of the most widely cultivated fruit tree species of agricultural interest and it is the only species of the Vitis genus extensively used in the global wine industry
Evaluation trials have shown an overall high susceptibility to P. viticola infection, with some accessions showing a large distribution of the data (Supplementary Figure 1)
Experimental inoculations on 132 grapevine individuals belonging to the Mgaloblishvili seedling population and Georgian germplasm confirmed the high susceptibility of V. vinifera to P. viticola infection

Summary

Introduction

Vitis vinifera L. is one of the most widely cultivated fruit tree species of agricultural interest and it is the only species of the Vitis genus extensively used in the global wine industry. V. vinifera is known as the most susceptible Vitis species to Plasmopara viticola P. viticola was introduced into France from North America during the XIX century together with American wild Vitis species and rapidly spread across Europe dividing into two genetically distinct groups. New Downy Mildew Resistance Loci (Fontaine et al, 2013; Maddalena et al, 2020). Structure analysis indicated that the European and Italian P. viticola populations is formed by two separate genetic clusters, distributed according to a geographical gradient (East-West) and climatic conditions (Fontaine et al, 2013; Maddalena et al, 2020). P. viticola is a polycyclic pathogen able to biotrophically grow on tissues (leaves, shoots, and clusters) of susceptible Vitis species and, V. vinifera. If adequate disease management strategies are not applied, the disease seriously affects yield in terms of on grape quality and quantity (Toffolatti et al, 2018b)

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