Responses of Heterodera glycines and Meloidogyne incognita to exogenously applied biogenic amines

Abstract

AbstractHatching and head movement behaviours of second-stage juvenile (J2) of two agriculturally important plant-parasitic nematodes were affected by the in vitro application of biogenic amines. The behavioural responses of Heterodera glycines and Meloidogyne incognita to treatments of serotonin, octopamine and dopamine were qualitatively similar, but significant quantitative differences between the species were revealed. The frequency of J2 head movement was decreased by as little as 250 μM serotonin in H. glycines and 500 μM serotonin in M. incognita, with effective doses (ED50) of 0.73 mM for H. glycines and 1.72 mM for M. incognita. Octopamine had the opposite effect of serotonin, increasing J2 head movement frequency at thresholds of 2 mM in H. glycines and 1 mM in M. incognita. Octopamine ED50 values were 32.35 mM and 1.91 mM, respectively. Dopamine had no effect on head movement in either species up to concentrations of 20 mM. Serotonin inhibited hatch in both species but was more potent against H. glycines (90% inhibition at 1 mM) than M. incognita (40% inhibition at 5 mM). Octopamine reduced hatch equally in both species with over 95% inhibition at 80 mM. Dopamine had no effect on hatch in M. incognita but did inhibit H. glycines hatch over 60% at 40 mM. The value of detailed quantitative analyses of plant-parasitic nematode responses to biogenic amines for studies on nematode control is discussed.