Screening of tomato germplasm against root knot nematode (Meloidogyne incognita) and biochemical characterization of selected tomato genotypes

Forty genotypes of tomato were screened for their reaction to Meloidogyne incognita. Three genotypes were found to be resistant to the nematode species. Ten selected genotypes varying in their degree of resistance were inoculated with M. incognita and the phenolic profile and activities of different enzymes viz. phenylalanine ammonia lyase (PAL), peroxidase (PO) and catalase (CAT) were studied in leaves and roots at 50 days after inoculation. Biochemical analysis revealed higher total phenols, orthodihydroxyphenols, flavonols, PAL and POD activity in leaves and roots of resistant genotypes than in susceptible genotypes whereas CAT activity showed the reverse trend. Among the various genotypes, Hisar Lal registered higher total phenols, PAL and PO activities in leaves whereas Line 82125 showed higher orthodihydroxyphenols, flavonols and PO activity in roots compared to other genotypes inoculated with M. incognita. Higher expression of PO and PAL enzymes/phenolic constituents in resistant genotypes than susceptible genotypes is suggestive of their role in development of resistance in tomato against root knot nematode infection caused by M. incognita.