Effect of Rj - genotype and cultivation temperature on the 3 community structure of soybean - nodulating bradyrhizobia 4 5 6

23 The nodulation tendency and community structure of indigenous bradyrhizobia on 24 Rj-genotype soybean cultivars at cultivation temperatures of 33/28°C, 28/23°C and 23/18°C, 25 16/8 h (day/night degrees, hours) were investigated using 780 bradyrhizobial DNA samples 26 from an Andosol with 13 soybean cultivars of four Rj-genotypes (non-Rj, Rj2Rj3, Rj4 and 27 Rj2Rj3Rj4). A dendrogram was constructed based on restriction fragment length polymorphism 28 of the polymerase chain reaction products (PCR-RFLP) of the 16S-23S rRNA gene internal 29 transcribed spacer (ITS) region. Eleven Bradyrhizobium USDA strains were used as a 30 reference. The dendrogram indicated seven clusters based on similarities among the reference 31 strains. The occupancy rate of Bj123-cluster decreased with increasing cultivation temperature, 32 while the occupancy rates of Bj110-cluster, Be76-cluster and Be94-cluster increased with 33 increasing cultivation temperature. Especially, the Rj2Rj3Rj4-genotype soybeans were infected 34 with a number of Bj110-cluster, regardless of the increasing cultivation temperature, compared 35 with other Rj-genotype soybean cultivars. The ratio of beta diversity to gamma diversity 36 (H’β/H’γ), which represents differences in the bradyrhizobial communities by pair-wise 37 comparison among cultivation temperature sets within the same soybean cultivar, indicated 38 that the bradyrhizobial communities tended to be different among cultivation temperatures. 39 Multidimensional scaling (MDS) analysis indicated that the infection of Bj110-cluster and 40 Bj123-cluster by host soybean genotype and cultivation temperature affected the 41 bradyrhizobial communities. These results suggested that the Rj-genotypes and cultivation 42 temperatures affected the nodulation tendency and community structures of 43 soybean-nodulating bradyrhizobia. 44 on July 8, 2017 by gest ht://aem .sm .rg/ D ow nladed fom