Natural Resistances to Viruses in Cucurbits

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.

Grafting Snake Melon [Cucumis melo L. subsp. melo Var. flexuosus (L.) Naudin] in Organic Farming: Effects on Agronomic Performance; Resistance to Pathogens; Sugar, Acid, and VOC Profiles; and Consumer Acceptance

“…The aphid-transmitted Potyvirus WMV was the most prevalent, but another potyvirus, ZYMV, and the Begomovirus ToLCNDV were also found with a lower incidence. Resistances to all these viruses are available (Sáez et al, 2017;Pérez-de-Castro et al, 2019;Martín-Hernández and Picó, 2021), but have not been introgressed into the snake melon background. Therefore, introgression programs are needed to develop snake melon cultivars with resistance to these viruses.…”

Resistance to Cucumber Green Mottle Mosaic Virus in Cucumis melo

“…Equally susceptible as most Spanish landraces were also most of the accessions of Asian origin that belong to many melon groups such as ameri, Dudaim, even certain wild types (wild agrestis accessions PI 164797, PI 185111 or PI 536476) and Kachri (PI 614521), groups, where resistance had been previously described. Other melon accessions that were susceptible to both main virus isolates were some Indian accessions of momordica and conomon that otherwise are multi-resistant to other viruses: Shiro Uri Okayama, which is resistant to cucumber mosaic virus (CMV) [23], accession PI 124112, which is resistant to cucurbit aphid-born yellows virus and tomato leaf curl New Delhi virus [13] and momordica PI 180280, which is resistant to papaya ringspot virus and other potyviruses [17,24,25]. Rajamony et al, found mild symptoms when they inoculated Kachri melons [16].…”

“…The chinensis Korean accession PI 161375 "Sonwang Charmi" and the flexuosus melon BGV004853 showed the opposite behavior, expressing strong symptoms with the European isolate after 21 dpi, and intermediate symptoms with the Asian isolate after 14 dpi. PI 420176 and PI 161375 are resistant to CMV and multiresistant, respectively [13,27]. The resistance to CMV, however, is dependent on the strain of the virus, which constitutes another example of the importance of considering different viral strains in the characterization of resistance in plants [28].…”

“…Resistance is an important factor that determines concentrations of virus in several virus-cucurbits host plant pathosystems. This happens, for example, with cucurbit yellow stunting disorder virus and Watermelon mosaic virus in melon [11][12][13]. However, in the case of CGMMV, there is an urgent need for resistant melon cultivars that have restricted movement and replication of virus as well as reduced symptom development.…”

Resistance to Three Distinct Begomovirus Species in the Agronomical Superior Tropical Pumpkin Line AVPU1426 Developed at the World Vegetable Center

“…SLCPV appears to be confined to the Philippines and Taiwan, though by the current species demarcation criterion should be regarded as a strain of SLCCNV. C. moschata is among the domesticated Cucurbita species (C. pepo L., C. maxima Duchesne, C. moschata, C. argyrosperma Huber, and C. ficifolia Bouché), the one in which more resistances to viruses have been reported [18]. Certain C. moschata accessions have been used as sources of resistance to potyviruses and cucumoviruses [19,20], and commercial F1 hybrids of C. pepo have been developed by transferring the virus resistance genes from C. moschata [21,22].…”