IDENTIFICATION OF SYMBIOTIC GENES IN PEA (PISUM-SATIVUM L) BY MEANS OF EXPERIMENTAL MUTAGENESIS

Treatment with ethyl metanesulfonate was used for producing three symb iotic mutants of pea (Pisum sativum L.) with Nod- phenotype and one mu tant with Fix-phenotype. Hybrid analysis showed that the recessive mut ations in lines Sprint-2Nod- -1 and Sprint-2Nod--2, due to which plant s become incapable of nodulation and formation of vesicular-arbuscular mycorhiza, occurred in the previously described locus sym8. Cytologic al study of these mutants at the early stages of their infection by ro ot nodule bacteria revealed morphological changes in root hairs, which were apparently associated with inability of plants to be infected. I t was shown that Nod-phenotype of the mutants is not due to deficiency in flavonoid inducers of rhizobial genes in their root exudates. It w as also shown that the mutation leading to Fix- phenotype of the produ ced mutant line Sprint-2Fix- occurred in a previously unknown locus te ntatively designated symX. This gene was located in the third linking group of pea.