The role of Rhizobium sp., a rhizobacterium that produces exopolysaccharide in the aggregation of the rhizospherical soil of the sunflower: Effects on plant growth and resistance to hydric constraints

The aim of this work was to evaluate the contribution of roof-associated EP S-producing bacteria on the resistance of sunflower to water stress. We hav e isolated an EPS-prodrrcing strain, Rhizobium sp. YAS34, from sunflower rh izosphere. Experiments were carried out in pots up to seed maturity stage. Experimental design was a completely randomized block with two factors (ino culation vs water supply). As expected, water stress significantly decrease d plant growth at M1.1 stage and at maturity (-7%). This effect was associa ted with a lower number of seeds per plant (-7%), average weight of 1,000 s eeds (+ 13%) and grain oil yield (-18%). Root colonization of Rhizobium sp. YAS34 was validated by a significant increase of root-adhering soil and ag gregate stability of rhizospheric soil. The global effect of inoculation wa s evidenced on the percentage of oil in grains (+4%). The effect of inocula tion with Rhizobium sp. on the sunflower resistance to water stress has to be confirmed. These data suggest that Rhizobium could be used in associatio n with non-legumes crops to better control their water and nutrient uptake.