Comparative potential of Rhizobium species for the growth promotion of sunflower (Helianthus annuus L.)

Rhizobium besides its nodule formation characteristic with members of Fabaceae family has been recognized for its great root colonizing ability and growth hormone production potential. In addition to nitrogen fixation in legume plants, rhizobia considered as beneficial tools and act as plant growth promoting rhizobacteria (PGPR) with many non-legumes. Present study was elucidated to determine the comparative role of Rhizbium sp for growth promotion of sunflower. Rhizobia were isolated from five different legumes (mungbean, barseem, lentil, chickpea, and vegetable pea) and checked for their auxin production efficiency. Rhizobial isolates Cp-4 showed maximum auxin potential (5.37 µg mL -1 IAA equivalents).Results showed that inoculation of all rhizobial isolates caused significant increase in growth and physiological parameters of sunflower plants. While prominent results were found with inoculation of mungbean rhizobial isolate Mb-2 which increases the chlorophyll a, N, P, fresh and dry matter of sunflower significantly by 8.34, 4.9, 36, 31, and 34%, respectively in comparison to un-inoculated control plants. Hence, present study concluded that Rhizobium sp can be successfully used as PGPR in non-legumes after thorough investigations.