Evaluation of genetic and induced resistance phenomena in cucumbers against the root-knot nematode (Meloidogyne incognita)

Meloidogyne spp. is an important pest of cucurbits in tunnel farming of vegetables in Pakistan. A cucumber germplasm was evaluated for resistance against the root-knot nematode (RKN, Meloidogyne incognita) based on the number of galls and egg masses recorded under glass house conditions. All the cucumber accessions showed varying responses towards the RKN inoculation. Out of the fifteen cucumber lines, two were found to be moderately susceptible to M. incognita, ten were susceptible while the other three were highly susceptible. For the management of the nematodes, resistance was induced in a highly susceptible cucumber accession (28294) by the application (both drench and foliar) of elicitors, i.e., salicylic acid (SA) and benzothiadiazole (BTH). The application of SA and BTH significantly enhanced the defence mechanism of the cucumber plants when compared to the control. Increased enzymatic activities in the cucumber plants as the result of the elicitor applications were determined through spectrophotometer to correlate the induced resistance. There was a significant increase in the enzymatic activities when compared to the control in the cucumber plants, which ultimately enhanced the resistance as there was a decrease in the number of galls and egg masses per plant. The enzymatic antioxidant activity was also found to increase in response to the nematode infection. Both SA and BTH were reported to play pivotal roles in inducing resistance in cucumber plants against M. incognita.