|Takeo Yamakawa||Last modified date：2019.07.26|
Associate Professor / Molecular Biosciences / Department of Bioscience and Biotechnology / Faculty of Agriculture
|1.||Takeo Yamakawa, Yuichi Saeki, Chapter 5: Inoculation Methods of Bradyrhizobium japonicum onSoybean in South-West Area of Japan, In A Comprehensive Survey of International Soybean Research - Genetics, Physiology, Agronomy and Nitrogen Relationships, Ed by James E. Board , INTECH, Pages: 83-114, 2013.02, [URL], Inoculation with efficient rhizobia at the ordinary dose does not increase appreciably the seed yield of soybean because the occupation ratio of the inoculated rhizobial strains in the nodules is very low due to competition with less efficient indigenous rhizobia (1, 2). In order to increase the seed yield by rhizobial inoculation, the occupation ratio of the inoculated strains must be increased. The increase of the occupation ratio has been examined from various viewpoints such as improvement of inoculation method (3). For the screening of efficient and competitive strains, a large number of useful strains had been isolated from mutagenized and recombinant rhizobia (4, 5, 6).
Furthermore, Williams and Lynch (7) who identified a non-nodulating line of soybean among the progenies from the cross between cvs. Lincoln and Richard, showed that the abnormal nodulation reaction was controlled by a single recessive gene of the host plant, rj1. Thereafter, cv. Hardee was found to nodulate ineffectively with Bradyrhizobium japonicum belonging to the strains 3-24-44 and 122 serogroups (8, 9). It was demonstrated that the ineffective nodulation was controlled by a host dominant gene, Rj2. Furthermore, this cultivar was found to nodulate ineffectively with the R. japonicum strain 33 due to the presence of another Rj-gene, Rj3 (10). Cvs. Hill and Amsoy 71 harbor a gene (Rj4) that was responsible for the ineffective nodulation. These Rj4-cultivars were nodulated ineffectively with B. japonicum strain 61 (11). Soybean plants harboring these Rj-genes (Rj-cultivars) were considered to restrict effective nodulation with appropriate serogroups of strains and to prefer certain types of rhizobia for nodulation. If this assumption holds true, planting of Rj-cultivars could increase the populations of rhizobial strains highly compatible with those cultivars in soils. Therefore, the relationship between the Rj-genotypes of soybean and the preference of the Rj-cultivars for various types of Bradyrhizobium strain was examined (12, 13). These Bradyrhizobium strains were classified into three nodulation types, type A, B, and C, based on the compatibility with Rj-cultivars. Nodulation type A strains nodulated with almost all the cultivars except for the rj1-ones (non-nodulating lines) and were preferred by non-Rj-ones. Type B or type C strains nodulated soybean cultivars other than the Rj2Rj3-ones or Rj4-ones, respectively except for rj1-ones and were preferred by Rj4-ones or Rj2Rj3-ones, respectively.
This chapter deals with the developmental process and experimental trial of inoculation methods using effective Bradyrhizobium strains and various Rj-genotypes to increase the yield of soybean.
|2.||Y. Saeki, M. Ikeda, T. Yamakawa and Y. Nagatomo, Basic Protocols for Soil Chemistry and Plant Nutrition Study., HAU-JICA ERCB Project, Hanoi, Vietnam, p.1-84, 2002.04.|