CHARACTERIZATION OF 2 CLASSES OF NONFIXING MUTANTS OF PEA-PLANTS (PISUM-SATIVUM L)

Seven (Nod(+)Fix(-)) mutants of pea cv. Frisson were isolated following ethylmethane sulphonate mutagenesis. Histological, fluorescence and molecular approaches have been used to characterize symbiotic phenotypes and to classify the mutants. In air cases, Rhizobium infection occurred via root hairs and resulting nodules had a typical indeterminate structure. However, mutants could be broadly classified into two group on the basis of nodule development and the level of nodule-specific gene transcripts. In the first groups, comprising P12, P58, P61 and P63 lines, nodule development was approximately normal but was followed by premature senescence. In the second group comprising P59, P60 and P62, mutant lines showed an early arrest of nodule development. Developmentally-defective root hairs were also observed on roots of mutant P62.