Resistance of Cucurbita maxima ‘Exposição’ to zucchini lethal chlorosis virus is likely associated with restriction to the systemic movement of the virus

Abstract

Zucchini lethal chlorosis virus (ZLCV), genus Orthotospovirus, so far was only reported in Brasil. The main natural hosts of ZLCV are in the cucurbit family. Pumpkin (Cucurbita maxima) cultivar Exposição was previously reported as highly resistant to ZLCV infection. The objectives of this work were to better characterize the resistance of the Exposição cultivar to ZLCV and to evaluate the interference of potyviruses (papaya ringspot virus type W, PRSV-W, and zucchini yellow mosaic virus, ZYMV) in the ZLCV resistance of this cultivar. C. maxima ‘Exposição’ and zucchini (C. pepo) ‘Caserta’ (susceptible control) plants were mechanically inoculated with ZLCV in the cotyledons. Resistance to infection and systemic virus movement were evaluated at 7 and 20 days later. Virus detection was performed using PTA-ELISA and RT-PCR in the cotyledons and upper leaves. The interference of the potyviruses in ZLCV resistance was evaluated in greenhouse and field assays. ZLCV was detected in the inoculated cotyledons of both cultivars, but it did not move systemically in C. maxima ‘Exposição’. The potyviruses PRSV-W and ZYMV did not interfere in the response of C. maxima ‘Exposição’ to infection with ZLCV. The resistance of ‘Exposição’ to ZLCV can be explored in future cucurbitaceae breeding programs.