[Genetic and physiological compatibility of different forms of the stem eelworms. V. The crossing of the red clover race with other eelworms].

Reciprocal hybrids between the stem eelworm of the red clover and those of onion, straw berry, parsnip, parsley and narcissus were obtained. Observations were conducted on the state of hybrid and control populations within 10 generations. A partial genetic and physiologica incompatibility of crossed forms of stem eelworms which manifests itself to a different extent in various combinations of parental pairs, was revealed. The red clover eelworm is a biological race of the collective species Ditylenchus dipsaci, which is at a certain stage of intraspecific differentiation.