Abstracts |
The population dynamics of naturally-occurring antibiotic producing and nitrogen
fixing rhizobacteria, as well as of arbuscular mycorrhizal fungi (AMF) was investigated for a
hybrid of maize (Lo964 x Lo1016) in comparison to its two parental lines (Lo964 and Lo1016),
during four successive 5-week-long growth cycles in the same pot. Beneficial rhizobacteria, such
as nitrogen fixers and 2,4-diacetylphlorolziucinol (DAPG) and pyrrolnitrin (PRN) producers, as
well as AMF were stimulated in the hybrid rhizosphere earlier than in those of the two parental
lines. In fact, they were molecularly detected in all rhizospheric samples of the hybrid,
independently of the cycle, whereas for the parental lines positive detections occurred only for
samples collected after at least two growth cycles. Interestingly, a MPN-PCR approach on
rhizospheric DNA samples indicated that, when detected, beneficial rhizobacteria reached similar
density in all maize genotypes (2 x 10(3) to 2.2 x 10(4) target DNA sequences/g(-1) of root).
Concerning the AMF, even if the three maize genotypes were cultivated in the same soil, it
appears that each maize genotype stimulates the AMF population differently. Both the hybrid and
the Lo964 line were able to select, in the observed time period, their own adapted phylogenetic
AMF subgroups (Glomus A for the hybrid. Archeospora for Lo964), whereas the Lo1016 line was not.
(c) 2007 Elsevier Ltd. All rights reserved. |