Effects of Meloidogyne incognita, Pectobacterium betavasculorum and Rhizoctonia solani interactions on growth, physiological and biochemical changes of beetroot

Effect of Meloidogyne incognita, Pectobacterium betavasculorum and Rhizoctonia solani alone, pre, post and simultaneous inoculations to find out role of each pathogen on growth, chlorophyll and carotenoid, superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), ascorbate peroxidase (APX), glutathione peroxidase (GPX), glutathione reductase (GR) activities and proline, H2O2 and malondialdehyde (MDA) of beetroot (Beta vulgaris L). Inoculation of plants with M. incognita / P. betavasculorum or R. solani reduced plant growth (root dry weight) (42.0%), chlorophyll (24.2%) and carotenoid (47.7%) while inoculation of pathogens under study resulted in increased activities of antioxidant enzymes, proline, H2O2 and MDA. Combined inoculation of pathogens under study resulted in greater reduction of plant growth (74.9%), chlorophyll (55.3%) and carotenoid (83.7%) than individual pathogen. Greatest reduction in plant growth, chlorophyll and carotenoid and maximum activities of antioxidant enzymes, proline, H2O2 and MDA were observed when M. incognita was inoculated 20 days prior to P. betavasculorum plus R. solani. P. betavasculorum and R. solani reduced galling and nematode multiplication but maximum reduction in galling (82.8%) and nematode multiplication (82.7%) was observed when P. betavasculorum plus R. solani were inoculated prior to nematodes. Necrosis soft rot and root rot indices by P. betavasculorum and R. solani were 3 respectively. Disease indices were 5 when two or more pathogens were inoculated together. Prior inoculation of M. incognita predisposed beetroots to P. betavasculorum and R. solani and aggravates the disease.