Selection of type A and type B strains for improving symbiotic effectiveness on non<i>-Rj</i> and <i>Rj</i><sub>4</sub> genotype soybean varieties
Creators: name: Aung Zaw Htwe
name: Yamakawa, Takeo
Publisher: name: Taylor & Francis
Year: 2018
Subjects: subject: Biochemistry
subject: Microbiology
subject: FOS: Biological sciences
subject: FOS: Biological sciences
subject: Cell Biology
subject: 59999 Environmental Sciences not elsewhere classified
subject: FOS: Earth and related environmental sciences
subject: FOS: Earth and related environmental sciences
subject: Ecology
subject: 69999 Biological Sciences not elsewhere classified
subject: Plant Biology

description: The selection of effective rhizobia for higher efficiency nitrogen fixation is one of the most important steps for inoculant production. Therefore, this experiment was conducted to select the most effective type A and type B strains for specific <i>Rj</i>-gene harboring soybean varieties and to test the symbiotic effectiveness of selected strains on different <i>Rj</i>-gene harboring soybean varieties. Screening experiments using the specific soybean varieties were done with a completely randomized design and three replications in this study. Evaluation of the effective Myanmar <i>Bradyrhizobium</i> strains for plant growth, nodulation and N<sub>2</sub> fixation were studied in pot experiments using sterilized vermiculite in the Phytotron (controlled-environmental condition). Then, a pot experiment was conducted using Futsukaichi soil in the screen house (natural environmental condition). The N<sub>2</sub> fixation ability of soybean was evaluated by acetylene reduction activity (ARA) and the relative ureide index method. In the first screening experiment, type A and type B strains with higher nitrogen fixation and proper nodulation on their respective soybean cultivars were selected for the next screening. In the second screening, <i>Bradyrhizobium elkanii</i> AHY3-1 (type A), <i>Bradyrhizobium japonicum</i> SAY3-7 (type A), <i>B. elkanii</i> BLY3-8 (type B) and <i>B. japonicum</i> SAY3-10 (type B) isolates, which showed higher nitrogen fixation and nodulation in Yezin-3 (<i>Rj</i><sub>4</sub>) and Yezin-6 (non-<i>Rj</i>), were selected for the next experiment. In the third screening experiment, SAY3-7 and BLY3-8, which had higher nitrogen fixing potential and proper nodulation, were selected as effective isolates. These two isolates were compatible with non<i>-Rj</i> and <i>Rj</i><sub>4</sub> soybean varieties for nodulation and nitrogen fixation. Based on the results of the screening experiment, these two strains were tested for their symbiotic efficacy in Futsukaichi soil. This study shows that inoculation treatment of SAY3-7 and BLY3-8 significantly increased plant growth, nodulation, and N<sub>2</sub> fixation at the V6, R3.5 and R8 stages in Yezin-3 (<i>Rj</i><sub>4</sub>) and/or Yezin-6 (non<i>-Rj</i>), and the seed yield at R8 stage, in Yezin-3 (<i>Rj</i><sub>4</sub>) and Yezin-6 (non<i>-Rj</i>) soybean varieties compared with the control treatment. It can be concluded that SAY3-7 and BLY3-8 are suitable for inoculant production because of their higher nitrogen fixation ability, proper nodulation and better productivity of Myanmar soybean cultivars.