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ScienceDaily: New Plant-bacterial Symbiotic Mechanism Promising For Crop Applications

New Plant-bacterial Symbiotic Mechanism Promising For Crop Applications

Science Daily — The growth of most plants depends on the presence of sufficient amounts of nitrogen contained in the soil. However, a family of plants, the legumes, is partially free of this constraint thanks to its ability to live in association with soil bacteria of the Rhizobium, genus, capable of fixing nitrogen from the air
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The team from the IRD's 'Laboratoire des Symbioses Tropicales et Méditerranéennes' and its partners taking as model a symbiosis between a tropical aquatic legume, Aeschynomene, and Bradyrhizobium, bacteria of the Rhizobia family, have just revealed a new mode of communication at molecular level between these two organisms. The bacteria of this original model have their own photosynthetic pathway, a unique property in the rhizobia. This special character confers on it the exceptional, rare ability to form nodules on the stems of its host-plant. The plant thus acquires the possibility of fixing much higher quantities of nitrogen than those usually measured in leguminous plants which have nodules only on their roots.

More on pesticides and fertility.

"Our research provides another explanation for declining crop yields," Fox said. "We showed that by applying pesticides that interfere with symbiotic signaling, the overall amount of symbiotic nitrogen fixation is reduced.
If this natural fertilizer source is not replaced by increased application of synthetic nitrogen fertilizer, then crop yields are reduced and/or more growing time is needed for these crops to reach the yields obtained by untreated crops.
We feel that this is a previously unforeseen factor contributing to declining crop yields."

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Alfalfa roots secrete chemical signals into soil to attract and recruit bacteria. These bacteria live in a plant's roots and provide a natural fertilizer source. Pictured is an alfalfa root with root hairs that have attracted rhizobia soil bacteria, which are engineered to appear in green fluorescence for easier visualization. (Credit: Image courtesy of Jennifer E. Fox)