Abstract
Infection threads are important for symbiotic nitrogen fixation of legumes such that the structure is a pathway of rhizobia infected from rhizosphere to plant cells. With the aim of identifying the factors involved in infection thread development molecular-genetically, we have isolated and analyzed symbiotic mutants of Lotus japonicus that show defect in the development. We have identified 5 complementation groups of B-129 background, and carried out fine mapping using MG-20 as a crossing partner. Of these, Ljsym74 and Ljsym80 were mapped in LG1, Ljsym82 and Ljsym84 in LG2, and Ljsym79 in LG5. Mapping of Ljsym74 locus was further investigated using B-303 as a crossing partner, because the locus was initially mapped at the co-segregated 0cM region between B-129 and MG-20 due to the translocation event. By phenotype analysis, those mutants were categorized in two aspects of infection thread behavior; point of abortion and structure.
