An Inducible Activator Produced By A Serratia Proteamaculans Strain And Its Soybean Growth-Promoting Activity Under Greenhouse Conditions
An inducible activator produced by a Serratia proteamaculans strain and its soybean growth-promoting activity under greenhouse conditions
Yuming Bai, Alfred Souleimanov and Donald L. Smith1
Department of Plant Science, Macdonald Campus of McGill University, 21,111 Lakeshore Road, Ste Anne de Bellevue, Quebec, Canada H9X 3V9
Received 23 October 2001; Accepted 20 February 2002
Astract
Serratia proteamaculans 1-102 (1-102) promotes soybeanbradyrhizobia nodulation and growth, but the mechanism is unknown. After adding isoflavonoid inducers to 1-102 culture, an active peak with a retention time of about 105 min in the HPLC fractionation was isolated using a bioassay based on the stimulation of soybean seed germination. The plant growth-promoting activity of this material was compared with 1-102 culture (cells) and supernatant under greenhouse conditions. The activator was applied to roots in 83, 830 and 8300 HPLC microvolts (µV) per seedling when plants were inoculated with bradyrhizobia or sprayed onto the leaves in same concentrations at 20 d after inoculation. The root-applied activator, especially at 1 ml of 830 µV per seedling, enhanced soybean nodulation and growth at the same level as 1-102 culture under both optimal and sub-optimal root zone temperatures. Thus, this activator stimulating soybean seed germination is also responsible for the plant growth-promoting activity of 1-102 culture. However, when sprayed onto the leaves, the activator did not increase growth and in higher concentrations decreased average single leaf area. The results suggest that this inducible activator might be a lipo-chitooligosaccharide (LCO) analogue. LCOs act as rhizobia-to-legume signals stimulating root nodule formation. The activator could provide additional signal', increasing in the signal quality (the signal-to-noise ratio, SNR) of the plantrhizobia signal exchange process.
Key words: Inducible activator, plant...
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