The effects of root exudate (RE) treatment on nodule occupancy by @entity19062 were investigated by a rapid colored-nodule assay, which is based on the observation that @entity19063 L-110 and its antibiotically marked derivatives form dark-red nodules on certain @entity1460 ( @entity1460 ) cultivars, whereas other strains form beige nodules. The efficacy of the assay was confirmed by direct immunofluorescence and by antibiotic platings of nodule bacteria. Both logarithmic- and stationary-phase cultures of the reference strain, L-110Nal, were used in paired-competition studies with RE-treated or untreated cells of seven challenge strains. On the basis of field and greenhouse competition studies, these strains were placed into three competitiveness groups: high (AN-11, AN-16aStrRif, and @entity1278 ), intermediate ( @entity25291 and 122SR), and low (I-110ARS and AN-18). Seedlings of G. max cv. Centennial were inoculated with two ratios of challenge to reference strain, 1:1 and 1:9, and nodule occupancy was determined after the V4 to V5 stage of ontogeny. Two of the strains showed increased occupancy in response to RE treatment at the 1:1 inoculation ratio. Logarithmic- and stationary-phase cultures of @entity1278 showed increased occupancy, from 22 to 38% (P < 0.10) and from 23 59 39% (P < 0.05), respectively. While the maximum increase for stationary-phase cultures of AN-16aStrRif was from 34 to 47% (P < 0.05), logarithmic-phase cultures failed to respond to RE treatment. The results of these studies indicate that RE treatment increases the nodule occupancy of some, but not all, @entity19063 strains and that the colored-nodule assay could be rapidly and reliably used to determine the competitive ability of @entity19063 .

Rapid Colored-Nodule Assay for Assessing Root Exudate-Enhanced Competitiveness of XXXX .

@entity19063 :: ('373177', 'Species') :: ['B. japonicum'] @entity1278 :: ('MESH:D000856', 'Disease') :: ['AN-6'] @entity1460 :: ('3847', 'Species') :: ['soybean', 'Glycine max'] @entity19062 :: ('375', 'Species') :: ['Bradyrhizobium japonicum'] @entity25291 :: ('MESH:C039620', 'Chemical') :: ['AN-3']
@entity19062 :: (375,Species) :: ['Bradyrhizobium japonicum']
