Genetical factors concerned in the symbiosis of clover and nodule bacteria

In spite of their intrinsic biological and evolutionary interest the genetical factors involved in symbiotic relationships have received very little attention. In the allied field of parasitism, the need for restricting variability of the host in the interests of experimental work has concentrated rather more attention on the genetical aspects of the host-parasite relationship. This has been achieved by the breeding of disease-susceptible and resistant lines of plants or animals for use as hosts in the study of variability in the parasite ; but it is evident that correlated studies of variation in both host and parasite are required for a better understanding of the interrelations concerned in parasitism. In the case of insect-transmitted virus disease, Storey1 has shown that the interrelations are even more complex because the genetic constitution of the vector may also have to be taken into account. RESP-2569