cmv1-Mediated Resistance to CMV in Melon Can Be Overcome by Mixed Infections with Potyviruses

Resistance to cucumber mosaic virus (CMV) strain LS in melon is controlled by the gene cmv1, which restricts phloem entry. In nature, CMV is commonly found in mixed infections, particularly with potyviruses, where a synergistic effect is frequently produced. We have explored the possibility that this synergism could help CMV-LS to overcome cmv1-mediated resistance. We demonstrate that during mixed infection with a potyvirus, CMV-LS is able to overcome cmv1-controlled resistance and develop a systemic infection and that this ability does not depend on an increased accumulation of CMV-LS in mechanically inoculated cotyledons. Likewise, during a mixed infection initiated by aphids, the natural vector of both cucumoviruses and potyviruses that can very efficiently inoculate plants with a low number of virions, CMV-LS also overcomes cmv1-controlled resistance. This indicates that in the presence of a potyvirus, even a very low amount of inoculum, can be sufficient to surpass the resistance and initiate the infection. These results indicate that there is an important risk for this resistance to be broken in nature as a consequence of mixed infections, and therefore, its deployment in elite cultivars would not be enough to ensure a long-lasting resistance.

This research received funding from the European Union’s Horizon 2020 research and innovation program under Marie Šklodowska-Curie grant agreement no. 793,090 (awarded to AG). This paper is part of the R&D&I project RTI2018-097665-B-C21 to AMMH, funded by MCIN/AEI/10.13039/501100011033/ and “ERDF A way of doing Europe” and also of the project PID2019-105692RB-100 to JJLM, funded by MCIN/AEI/10. 13039/501100011033/. CRAG was also supported by grants SEV-2015-0533 and CEX2019-000902-S, funded by MCIN/AEI/10.13039/501100011033, and by the CERCA Program, Generalitat de Catalunya.

With funding from the Spanish government through the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000902-S).

Peer reviewed