Natural resistances to viruses in cucurbits

This article belongs to the Special Issue Recent Advances in Genomics, Genetic Resources Evaluation and Breeding of Cucurbitaceae Crops.Cucurbit viruses cause considerable economic losses worldwide. The most common viral diseases affecting this crop family are Potyviruses, Cucumoviruses, Criniviruses, Ipomoviruses, Tobamoviruses, and the emerging Begomoviruses. Four main cucurbit crops are grown worldwide, namely melon, cucumber (Cucumis), watermelon (Citrullus), and squash (Cucurbita). Huge natural variation is also available within each genus, providing valuable sources of genetic resistance to these diseases. Intraspecific and intrageneric diversity and crossability are key factors to select the optimum breeding strategies. Melon and cucumber are diverse species for which intraspecific resistance is available. Conversely, in Citrullus and Cucurbita, wild relatives provide the resistance diversity absent in watermelon and in C. pepo. Some of the classical sources used by breeders, many of which are multi-resistant, come from corresponding origin centers in Asia, Africa, and America, as well as from secondary centers of diversity. Genetic studies have identified dominant and recessive and often complex resistance. Many of the genes identified have been mapped and markers for MAS are available, but higher mapping resolutions are required to identify the corresponding genes. Only a few genes could be cloned and functionally characterized. Efforts are underway to use genome mapping and functional genomics to advance toward a genomic-assisted breeding against viral diseases in cucurbits.AMM-H was supported by by the Ministerio de Ciencia, Innovación y Universidades, cofunded with FEDER funds, grant RTI2018-097665-B-C21-R. We acknowledge financial support from the Spanish Ministry of Economy and Competitiveness, through the “Severo Ochoa Programme for Centres of Excellence in R&D” 2016–2019 (SEV-2015-0533) and the CERCA Programme/Generalitat de Catalunya. BP was supported by the Ministerio de Ciencia, Innovación y Universidades, cofunded with FEDER funds project AGL2017-85563-C2-1-R, and by PROMETEO project 2017/078 (to promote excellence groups) by the Conselleria d’Educació, Investigació, Cultura i Esports (Generalitat Valenciana)Peer reviewe