Establishment of Azorhizobium caulinodans in the rhizosphere of wetland rice (Oryza sativa L.) |
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| Authors: | C Van Nieuwenhove L Van Holm S A Kulasooriya K Vlassak C Van Nieuwenhove L Van Holm |
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| Institution: | (1) Faculty of Agricultural and Applied Biological Sciences, Laboratory of Soil Biology and Soil Fertility, Kard. Mercierlaan 92, B-3001 Heverlee, Belgium e-mail: catherine.nieuwenhove@agr.kuleuven.ac.be Fax: +32-16-321997, BE;(2) Faculty of Science, Department of Botany, University of Peradeniya, Sri Lanka, LK;(3) Institute of Fundamental Studies, Kandy, Sri Lanka, LK |
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| Abstract: | Azorhizobium caulinodans strongly colonized the rhizosphere of rice plants after incorporation of Sesbania rostrata in a field trial throughout the growing season and during the fallow period until 19 weeks after incorporation of S. rostrata. A. caulinodans became well established in the rhizosphere (7.17 log cfu g–1 dry rice root) and colonized subsequent S. rostrata test plants. Three traditional and three improved high-yielding rice varieties were inoculated with A. caulinodans under gnotobiotic conditions. In none of the combinations did acetylene reduction activity significantly increase. Ethylene
production on colonized rice roots only started after the growth medium had been supplemented with an extra C source (0.1
to 0.25% Na-lactate). This indicates that the bacterial nitrogenase activity is limited by energy supply. Four possible inoculant-carriers
(peat, coir dust, bagasse, rice straw) were compared for long-term survival of the bacterial strain. Independent of the storage
temperature (26 °C or 4 °C), the survival of A. caulinodans in peat and coir dust was very high during a 12-month period (>8 log cfu g–1 dry carrier), whereas the bagasse and rice straw carriers showed a serious decline from 3 months onwards.
Received: 6 April 1999 |
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| Keywords: | Azorhizobium caulinodans Rice Inoculum survival Inoculum carriers Sesbania rostrata |
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