The interaction of SO 2 and root-knot nematode on tomato

Abstract

Intermittent exposure of tomato plants (cv. Pusa Ruby) to SO 2 at 286 μg m −3 (3 h every heavy third day for 75 days) induced slight chlorosis of leaves. At 571 μg m −3, considerable chlorosis with browning developed on the foliage. These symptoms were more pronounced and appeared earlier on SO 2-exposed plants infected with Meloidogyne incognita race 1 (Mi), especially in post- and concomitant-inoculation exposures. Mi and/or SO 2 significantly reduced different parameters of plant growth. Synergistic (positive) interactions between SO 2 and Mi occurred in concomitant- and post-inoculation exposures at 286 and 571 μg m −3, respectively. In other treatments, an antagonistic (negative) interaction was observed. However, in a few cases, additive effects of SO 2 and Mi were also recorded. Intensity of root-knot (galling) was enhanced at both concentrations of SO 2, while reproduction (egg mass production) of Mi was enhanced in concomitant-inoculation exposures at 286 μg m −3 and inhibited at 571 μ m −3. Exposure to SO 2 and/or Mi decreased the number and size of stomata but increased the number and length of trichomes on both the leaf surfaces. Stomatal aperture was significantly wider in the plants exposed to 571 μg SO 2 m −3 alone and in pre-, post-, and concomitant-inoculation exposures at 286 or 571 μg m −3. Stomatal aperture was directly related to foliar injury and reductions in growth, yield, and leaf pigments.