Mapping Cucumber Vein Yellowing Virus Resistance in Cucumber (Cucumis sativus L.) by Using BSA-seq Analysis.

Marta Pujol,Konstantinos G Alexiou,Patricia Mayor,Torben Jahrmann,Jordi Garcia-Mas,Miguel A Aranda,Manuel Miras,Anne-Sophie Fontaine

doi:10.3389/fpls.2019.01583

Abstract

Cucumber vein yellowing virus (CVYV) causes severe yield losses in cucurbit crops across Mediterranean countries. The control of this virus is based on cultural practices to prevent the presence of its vector (Bemisia tabaci) and breeding for natural resistance, which requires the identification of the loci involved and the development of molecular markers for linkage analysis. In this work, we mapped a monogenic locus for resistance to CVYV in cucumber by using a Bulked Segregant Analysis (BSA) strategy coupled with whole-genome resequencing. We phenotyped 135 F3 families from a segregating population between a susceptible pickling cucumber and a resistant Long Dutch type cucumber for CVYV resistance. Phenotypic analysis determined the monogenic and incomplete dominance inheritance of the resistance. We named the locus CsCvy-1. For mapping this locus, 15 resistant and 15 susceptible homozygous F2 individuals were selected for whole genome resequencing. By using a customized bioinformatics pipeline, we identified a unique region in chromosome 5 associated to resistance to CVYV, explaining more than 80% of the variability. The resequencing data provided us with additional SNP markers to decrease the interval of CsCvy-1 to 625 kb, containing 24 annotated genes. Markers flanking CsCvy-1 in a 5.3 cM interval were developed for marker-assisted selection (MAS) in breeding programs and will be useful for the identification of the target gene in future studies.

Highlights

Cucumber vein yellowing virus (CVYV) is an ipomovirus that is transmitted in a semi-persistent manner by the whitefly Bemisia tabaci
The uniformity of symptoms in plants from each accession was remarkable, and each accession could be assigned to a symptom severity class without uncertainty for each observation time-point
The progression of the disease was very much reduced as compared to susceptible controls, the growth of the plants was not affected at all, and viral accumulation was significantly reduced as compared to PS and F1 plants

Summary

Introduction

Cucumber vein yellowing virus (CVYV) is an ipomovirus (family Potyviridae) that is transmitted in a semi-persistent manner by the whitefly Bemisia tabaci. CVYV infects cucurbits, causing symptoms of variable intensity. In cucurbit-producing areas of heavy B. tabaci infestation, it can Mapping CVYV Resistance by BSA-seq cause epidemics with massive yield losses and dramatic economic consequences. Picó et al, 2003) and commercial seed companies are currently selling cucumber hybrids resistant to CVYV, which represent an excellent solution for disease control. Varieties and hybrids seem to share the common characteristic that resistance is partial; symptoms in inoculated plants are mild or absent, and the virus can be detected infecting systemically the so-called resistant plants, at reduced levels as compared to susceptible controls Varieties and hybrids seem to share the common characteristic that resistance is partial; symptoms in inoculated plants are mild or absent, and the virus can be detected infecting systemically the so-called resistant plants, at reduced levels as compared to susceptible controls (e.g. Galipienso et al, 2013)

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