Evaluation ofCucurbita moschata×Cucurbita maximarootstocks against ToLCNDV

Abstract

Tomato leaf curl New Delhi virus (ToLCNDV) was first detected in Spain in 2012-2013. Currently, it causes major economic losses in zucchini (Cucurbita pepo), and until now no resistant or tolerant sources have been found in this species. Although in general less harmful, this begomovirus also infects other Cucurbita species, such as C. maxima and C. moschata, whose hybrids are commonly used as rootstocks for grafting watermelons and melons. In the present study, we have screened a selection of C. maxima and C. moschata accessions and their corresponding hybrids against ToLCNDV using mechanical inoculation. Symptoms were scored at 15 and 30 days post inoculation (DPI), and the vulnerability index (Vul) was calculated. ToLCNDV was detected by PCR. At 30 DPI, all the C. moschata accessions had lower Vuls than the C. maxima accessions, which were more susceptible. This is consistent with previous studies that showed higher levels of resistance in some accessions of C. moschata. All accessions were ToLCNDV positive by PCR. Most of the evaluated hybrid progenies showed severe infections similar, or even more severe, to those found in their parentals. The great aggressiveness of this virus and the high susceptibility of the assayed hybrids can make the production of rootstocks difficult. Furthermore, the use of susceptible rootstocks to ToLCNDV can contribute to increase the severity of the infection in scions. Therefore the development of new rootstocks derived from selected tolerant C. moschata and C. maxima accessions might minimize this effect.