Ramongolalaina et al., 2018b

Additional QTLs controlling the genetic interrelationship between soybean with indigenious Bradyrhizobium japonicum strains in continuous monocropping

Clarissien Ramongolalaina1*, Teraishi Masayoshi1, Okumoto Yutaka1

1 Graduate School of Agriculture, Kyoto University, Oiwake, Kitashirakawa, Sakyo, Kyoto 606-8502, Japan

* Corresponding author (email: rclarss@gmail.com)

ABSTRACT

Symbiosis with a selectively nodulating rhizobium strain improve soybean productivity. However, in monocropping system the concentrations of root exudates, amongst them daidzein is one of the major secretions, might influence nodulating rhizobium communities and enable ineffective nitrogen fixation in soybean. We grew 93 recombinant inbred lines (RIL) of soybean seeds derived from the cross between Peking and Tamahomare in three cycles of successive cultivation and determined the bradyrhizobia nodulating each line using using PCR-RFLP analysis targeted to the 16S-23S rRNA gene internal transcribed spacer (ITS) region of the bacterial type of each root nodule. QTL analysis revealed two major QTL regions that control the competitiveness of Bradyrhizobium japonicum USDA110 the first on chromosome-18 and the second on chromosome-10. We also measured the amount of root-secreted daidzein of the one week old 93 RILs by HPLC analysis. QTL analysis showed a QTL region in chromosome-10 regulating root-secreted daidzein and coinciding with that controlling the competitiveness of B. japonicum USDA110. The root-secreted daidzein could be one of the major factors regulating the competitiveness of B. japonicum USDA110 to nodulate soybean under the dominance of B. elkanii in continuous mono-cropping system.