AUTHOR=Sáez Cristina , Martínez Cecilia , Montero-Pau Javier , Esteras Cristina , Sifres Alicia , Blanca José , Ferriol María , López Carmelo , Picó Belén 

TITLE=A Major QTL Located in Chromosome 8 of Cucurbita moschata Is Responsible for Resistance to Tomato Leaf Curl New Delhi Virus

JOURNAL=Frontiers in Plant Science

VOLUME=11

YEAR=2020

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2020.00207

DOI=10.3389/fpls.2020.00207

ISSN=1664-462X

ABSTRACT=<p><italic>Tomato leaf curl New Delhi virus</italic> (ToLCNDV) is a bipartite whitefly transmitted begomovirus, responsible since 2013 of severe damages in cucurbit crops in Southeastern Spain. Zucchini (<italic>Cucurbita pepo</italic>) is the most affected species, but melon (<italic>Cucumis melo</italic>) and cucumber (<italic>Cucumis sativus</italic>) are also highly damaged by the infection. The virus has spread across Mediterranean basin and European countries, and integrated control measures are not being enough to reduce economic losses. The identification of resistance genes is required to develop resistant cultivars. In this assay, we studied the inheritance of the resistance to ToLCNDV previously identified in two <italic>Cucurbita moschata</italic> accessions. We generated segregating populations crossing both resistant pumpkins, an American improved cultivar Large Cheese (PI 604506) and an Indian landrace (PI 381814), with a susceptible <italic>C. moschata</italic> genotype (PI 419083). The analysis of symptoms and viral titers of all populations established the same monogenic recessive genetic control in both resistant accessions, and the allelism tests suggest the occurrence of alleles of the same <italic>locus</italic>. By genotyping with a single nucleotide polymorphism (SNP) collection evenly distributed along the <italic>C</italic>. <italic>moschata</italic> genome, a major quantitative trait locus (QTL) was identified in chromosome 8 controlling resistance to ToLCNDV. This major QTL was also confirmed in the interspecific <italic>C. moschata</italic> × <italic>C. pepo</italic> segregating populations, although <italic>C. pepo</italic> genetic background affected the resistance level. Molecular markers here identified, linked to the ToLCNDV resistance <italic>locus</italic>, are highly valuable for zucchini breeding programs, allowing the selection of improved commercial materials. The duplication of the candidate region within the <italic>C. moschata</italic> genome was studied, and genes with paralogs or single-copy genes were identified. Its synteny with the region of chromosome 17 of the susceptible <italic>C. pepo</italic> revealed an INDEL including interesting candidate genes. The chromosome 8 candidate region of <italic>C. moschata</italic> was also syntenic to the region in chromosome 11 of melon, previously described as responsible of ToLCNDV resistance. Common genes in the candidate regions of both cucurbits, with high- or moderate-impact polymorphic SNPs between resistant and susceptible <italic>C. moschata</italic> accessions, are interesting to study the mechanisms involved in this recessive resistance.</p>