Effect of root nitrogen supply forms on attraction and repulsion of second-stage juveniles of Meloidogyne graminicola

Three experiments were conducted to compare the attraction and repulsion of second-stage juveniles (J2) of the root-knot nematode, Meloidogyne graminicola, to rice plants supplied with different forms of nitrogen. The rice plants were hydroponically grown in a full nutrient solution containing different concentrations (0.1 or 10.0 mM) of nitrate (NO3−) or forms of nitrogen supply (2.85 mM calcium nitrate (Ca(NO3)2), ammonium nitrate (NH4NO3) or ammonium chloride (NH4Cl)) for 2 weeks. Five rice plants were placed with their roots in one corner of a Perspex X or Y-chamber partly filled with agar and J2 were inoculated onto the chambers. The data show that J2 of M. graminicola were significantly attracted towards the roots of rice plants grown in hydroponics containing 0.1 mM NO3 − and 2.85 mM Ca(NO3)2, but repelled by 10.0 mM NO3 −, 2.85 mM NH4NO3 and NH4Cl. The results suggest that the application of ammonia-based nitrogen fertiliser to the rice nursery bed may interfere with nematode attraction and thus reduce invasion, and the application of chemical nitrification inhibitors to rice nursery beds may decrease nematode invasion.