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The infuence of native rhizobacteria on European alder (Alnus glutinosa (L.) Gaertn.) growth: II. Characterisation and biological assays of metabolites from growth promoting and growth inhibiting bacteria
F.J. Gutierrez Mañero, N. Acero, J.A. Lucas and A. Probanza
Plant and Soil
Vol. 182, No. 1 (May (I) 1996), pp. 67-74
Published by: Springer
Stable URL: http://www.jstor.org/stable/42946507
Page Count: 8
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Metabolite production was investigated in four bacterial strains that promoted (plant growth promoting rhizobacteria -PGPR-, B. licheniformis, isolate B. I2 and B. pumilus isolate B.3) or inhibited (deleterious rhizobacteria -DRB-, P. fluorescens bv II, isolates P.9 and P.20) growth of nodulated and non-nodulated Alnus glutinosa seedlings. These strains were isolated and characterized from the rhizosphere of a natural alder population, and their biological effects on plant growth determined on previous studies. Biological assays were performed to confirm the observed effects on aerial length (AL), aerial surface (AS), number of leaves (NL) and total nitrogen (TN). According to the high resolution gas chromatography (HRGC) results, PGPR strains produced auxin-like (IAA-1) compounds at levels of 1.736 and 1.790 mg IAA-1 L⁻¹ culture growth medium; however, they did not produce HCN. These compounds are derived from IAA and not from the Trp originated by peptide degradation in culture media. The promoting effect is evidenced when comparing the effects of IAA and the filtered bacterial growth culture medium to control (increases of 64% in aerial surface, 277% in total N content and 32% in aerial length). The deleterious strains produced HCN (1.6 and 2.4 mg kg⁻¹ detected in growth culture medium) and they did not produce IAA-1 compounds. The bacterial culture's -free of bacteria-inhibiting effects were 7% in aerial surface, 240% in total nitrogen content and 15% in aerial length. The results reported here suggest that the interactions that take place in the alder rhizosphere are in a delicate equilibrium. In view of this, the coexistence of PGPR and DRB strains in this environment is unquestionable, and does affect alder health in field conditions.
Plant and Soil © 1996 Springer