Tolerance to ToLCNDV in Cucurbita spp

Abstract

[EN] Tomato leaf curl New Delhi virus (ToLCNDV) is a bipartite begomovirus (Geminiviridae) firstly reported in India and neighboring countries. A severe outbreak of ToLCNDV in Zucchini (Cucurbita pepo) occurred in southern Spain in 2012. Mechanical inoculation and natural infection with Bemisia tabaci, in Almeria, were used to screen part of the COMAV's Cucurbita core collection. The tolerance was assessed by symptomatology and by a PCR-based diagnostic method that allows the detection of the two viral components in a single reaction. Mechanical transmission of ToLCNDV was confirmed in all the species. Severe symptoms were found 30 and 35 days after mechanical and natural inoculation, respectively, in C. pepo, in all accessions belonging to the Zucchini morphotype and to other morphotypes of the subsp. pepo, subsp. ovifera and even in the wild relative C. fraterna. Cucurbita maxima and C. ficifolia were also highly susceptible. The only species showing tolerance was C. moschata. Instead of curling, which was typically observed in most Cucurbita species, in C. moschata we observed mosaic and mottling, which suggest a differential response of this species. Under natural infection, a few C. moschata accessions remained asymptomatic and no virus was detected in the plant apex. Under mechanical inoculation, ToLCNDV symptoms were mild and delayed in these accessions and they were PCR positive. Some of the more tolerant accessions came from India.