Effect of elevated CO₂ on host-parasite relationship of Tomato and root-knot nematode, Meloidogyne incognita race 1

Tomato plants of two genotypes Pusa Ruby (susceptible) and SL-120 (resistant) were exposed to elevated CO₂ level of 550 ppm and root-knot nematode, (RKN) race 1 was inoculated on 15^th days of exposure. Histopathological studies revealed earlier development of RKN by the presence of adult female in Pusa Ruby on 20^th DAI and giant cells were observed in both resistant and susceptible genotypes. SL-120 succumbed to nematode attack and there was no any hypersensitive reaction noticed in infected cells. Significantly higher peroxidase (PO) and superoxide dismutase (SOD) activity was observed under elevated CO₂ and higher enzyme activity was observed at 3^rd DAI. Then, the enzyme activity started decreasing from 7^th up to 14^th DAI, irrespective of genotype and CO₂ exposure. Though higher enzyme activity was observed in resistant SL-120, the nematode continued to develop and complete its life cycle.