Natural Resistances to Viruses in Cucurbits

Ana Montserrat Martín-Hernández,Belén Picó

doi:10.3390/agronomy11010023

Abstract

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.

Highlights

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We exhaustively reviewed the current knowledge on natural resistances to viruses on the main four Cucurbitaceae crops, melon, cucumber, watermelon, and pumpkin and squash, as well as in wild relatives of the genera Cucumis, Citrullus, and Cucurbita
The range of resistance sources is diverse in the different cucurbits and in general resistances come from the same geographical regions, which coincide with the centers of origin, domestication, and diversification of the species

Summary

General Introduction

Plant viruses are responsible for more than USD 30 billion annual losses in crops [1], Received: 14 November 2020 Accepted: 21 December 2020 Published: 24 December 2020 and the economic impact of these pathogens is expected to increase under the current global warming scenario [2]. The major viruses affect all the main cucurbit crops, cucumber, melon, watermelon, zucchini, and pumpkin and squash, but some viruses are more damaging in specific crops. Others carry resistances to viruses of different families, like the Korean accession PI 161375, resistant to CMV, MNSV, KGMMV, and BPYV; the Indian PI 313970, resistant to CYSDV, CABYV, WmCSV, LIYV, and CuLCrV; and the African TGR-1551, resistant to WMV, CYSDV, and CABYV [21]. These accessions are very powerful genetic resources for pyramiding diverse resistances in elite cultivars (Table 1). Emerging viruses like ToLCNDV have become a serious problem in some regions, spreading throughout many countries

Other Cucumis Species

Findings

Conclusions and Perspectives