Molecular confirmation of ToLCNDV resistance in cucumber (Cucumis sativus L.) genotypes through agroinoculation and field screening

Abstract

Research was carried out to identify the source of resistance in four cucumber genotypes for ToLCNDV under natural field epiphytotic and greenhouse conditions. Over all the mean percent disease index and incidence ranged from 0 to 92.00% and 0 to 93.3% respectively. Under natural field conditions, the genotype DC 70 was found to be totally free from ToLCNDV infection followed by P-85 with 8.57 PDI and 28.57% disease incidence while DC 773 recorded 75.00 PDI and 87.50% disease incidence and DC 769 with 42.85 PDI and 71.42% disease incidence in rabi season under field epiphytotic condition. Similarly, during the kharif season the genotype DC 70 and P-85 were found to be totally free from ToLCNDV infection while DC 773 recorded 65.71 PDI and 85.00% disease incidence and DC 769 with 40.00 PDI and 75.00% disease incidence. Based on natural field evaluation the selected entries were subjected to artificial screening under greenhouse conditions. DC 70 was totally free from ToLCNDV infection upon artificial screening by agroinoculation. This was followed by P-85 with 22.91 PDI and 46.60% disease incidence and DC 773 recorded 92.00 PDI and 93.3%disease incidence. Symptomatic and asymptomatic leaves were confirmed for the presence of ToLCNDV by PCR assay. Susceptible genotypes expressed leaf curling, yellowing and severe mosaic on 28 days post-inoculation. Out of four genotypes screened, DC 70 showed highly resistant reaction and identified as reliable source of resistance for ToLCNDV in cucumber. The resistant source identified is a good candidate for resistant breeding for ToLCNDV in cucumber.