The influence of root diffusate, host age and water regimes on hatching ofthe root-knot nematode, Meloidogyne triticoryzae

The root-knot nematode, Meloidogyne triticoryzae, produces three kinds of u nhatched second stage juveniles (J2): i) those that hatch freely in water, ii) those that require stimulus from rice root diffusate (RRD), and iii) th ose that do not hatch even in the presence of RRD. The proportion of these three types varies with generation, with the final generation produced on s enescing plants having a large proportion of unhatched J2 of the third type , which is likely to equate with diapause. Dilution of RRD reduced its hatc hing activity and there is no evidence of the presence of inhibitors in the diffusate. The hatching response of M. triticoryzae may be modified additi onally by the growing conditions: submergence of infected plants may have d elayed hatch, possibly by causing anoxybiosis in unhatched J2, and thereby delayed the appearance of the second and third generations of the nematodes .