Serological and morphological studies on the inter- and intraspecific differences of the plant-parasitic nematodes Heterodera and Ditylenchus

Saline extracts of species of Ditylenchus and Heterodera initiated antibody production when inoculated separately into rabbits. On agar gel-diffusion plates these antisera gave a precipitate response against their homologous extracts and against extracts of some of the other nematode species. Up to four precipitation bands occurred, indicating the presence of at least four distinct antigens. Antisera to these extracts did not precipitate against extracts of the host plant or against the extracts of nematodes from other genera. None of the nematode extracts precipitated against normal serum. The precipitation response divided the Heterodera species tested into two groups, one containing H. schachtii, H. trifolii and H. rostochiensis and the other containing H. cruciferae, H. carotae and H. goettingiana with apparently no antigens common to both groups. The three species of Ditylenchus were serologically distinct, and it was not possible to interbreed D. myceliophagus and D. destructor. The extent of the postvulval sac was the most useful morphological character for separating D. myceliophagus from D. destructor. Only slight intraspecific serological differences were detected between five races (narcissus, oat, red clover, tulip and giant) of D. dipsaci and between the two pathotype populations (Colyton and Woburn) of H. rostochiensis. Precipitates occurred at the excretory pore of living larvae and adults of Ditylenchus species and at the vulval aperture of white females of Heterodera species placed in their homologous antisera.We thank Dr A. J. Gibbs for much advice.