Effect of soil bradyrhizobia on the success of soybean inoculant strain CB 1809.
Four decades of soybean [Glycine max (L.) Merr.] cultivation in South Africa has resulted in the establishment of populations of bradyrhizobia against which the recently introduced inoculant strain CB 1809 must compete. Serological and DNA fingerprinting methods were used to study the diversity of nodule isolates from soils at Bergville, Koedoeskop and Morgenzon. Dominant serogroups included Bradyrhizobium elkanii serotype 76 at Bergville (67%), Bradyrhizobium japonicum serotype 123 at Morgenzon (81%) and B. japonicum serotype 135 at Koedoeskop (100%). Their origin is unknown as they do not correspond in serotype to strains used in previous inoculants. A small percentage of isolates from Bergville (13%) and Morgenzon (16%) were serologically homologous to strain WB 1 (serotype 31/76), applied for two decades before CB 1809 (serotype 122). Nitrogen-fixing effectiveness of CB 1809 was superior to 60% of the isolates tested from Bergville and Morgenzon, but similar to 73% of the Koedoeskop isolates. Seed and liquid-in-furrow application methods increased CB 1809 nodule occupancy at least three-fold above background levels at Bergville (pH 5.16) and Morgenzon (pH 6.33). Inoculation did not, however, increase CB 1809 nodule occupancy at Koedoeskop (pH 7.76), possibly because alkaline soil conditions favoured the serotype 135 population predominant at this site.
ARC-Plant Protection Research Institute, Private Bag X134, Queenswood 0121, South Africa.
Wilhelm J
WJ
Botha
Julian B
JB
Jaftha
Jacomina F
JF
Bloem
Johannes H
JH
Habig
Ian J
IJ
Law
D020369:Bradyrhizobium / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification; D016172:DNA Fingerprinting / Q000379:methods; D021903:DNA, Ribosomal Spacer / Q000032:analysis; D008969:Molecular Sequence Data; D009586:Nitrogen Fixation; D010802:Phylogeny; D016133:Polymerase Chain Reaction; D012150:Polymorphism, Restriction Fragment Length; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D012338:RNA, Ribosomal, 23S / Q000235:genetics; D017422:Sequence Analysis, DNA; D012703:Serotyping; D012988:Soil Microbiology; D013019:South Africa; D013025:Glycine max / Q000382:microbiology*; D013559:Symbiosis
D021903:DNA, Ribosomal Spacer; D012336:RNA, Ribosomal, 16S; D012338:RNA, Ribosomal, 23S