Effect of Azospirillum brasilense inoculation on rhizobacterial ...

A. Lerner et al. / Soil Biology & Biochemistry 38 (2006) 1212–1218 1217
A
PC2 10%
Experiment 1
Week 1 Week 3
PC1 29%
Week 1 Week 3
Control
Exp 1 Exp 2
Experiment 2
A. <strong>brasilense</strong> Cd
A. <strong>brasilense</strong> Sp245
Exp 1 Exp 2
Exp 1 Exp 2
B
0.33 0.60 0.80 1.00
Cd11
245-11
245-12
245-10
C10
C12
C11
Cd12
Cd10
C14
Cd15
Cd13
C15
245-14
245-13
C13
245-15
Cd14
Week 1
Week 3
Fig. 3. Principle component analysis (PCA) based on ARISA (A) versus cluster analysis based on DGGE (B) <strong>of</strong> rhizosphere samples from a Haploxeralfs sandy soil.
The broken line separates the two experiments in the PCA. C, control; Cd, <strong>Azospirillum</strong> <strong>brasilense</strong> Cd; 245, Azospirilum <strong>brasilense</strong> Sp 245. Experiment 1, samples C,
Cd, and 245 numbers 4–6, week 1; 7–9, week 3 post-<strong>inoculation</strong>; experiment 2, samples C, Cd, and 245 numbers 10–12, week 1; 13–15, week 3 post-<strong>inoculation</strong>.
populations was plant age (Fig. 3(A)). Repeats <strong>of</strong> each
treatment were scattered in each <strong>of</strong> the two time points. No
effect <strong>of</strong> <strong>inoculation</strong> with A. <strong>brasilense</strong> could be detected.
These results are in very good correlation in with those
obtained using the 16S rDNA PCR-DGGE approach which
show that samples cluster according to plant age (Fig. 3(B)). In
each cluster the repeats were also randomly distributed.
In this study, we used different fingerprinting methods,
different primers sets for the same method and different
statistical approaches, yet similar results were obtained. We
are, therefore, confident to conclude that <strong>inoculation</strong> with A.
<strong>brasilense</strong> has no significant impact on the structure <strong>of</strong>
bacterial communities, at least when primers targeting the
eubacteria are used. In similar growth systems Herschkovitz