Relative potential of Rhizobium sp for improving the rice-wheat crop in the semi-arid regions

Abstract

Soil Microbiologists have been concentrating on manipulation of rhizosphere microbes in cereals, but many researchers have reported that rhizobia can act as plant growth promoting rhizobacteria (PGPR). Rhizobium species impacted the crop ontogeny by root / endophytic colonization, producing phytohormones, efficient nutrient use and nutrient solubilization / mineralization. Field studies were performed at Soil Bacteriology Section and Soil Chemistry Section, Faisalabad to assess the comparative potential of Rhizobium species for promoting the growth, yield of wheat and rice. Auxin biosynthesis potential of isolates of Rhizobium species (mung (Vigna radiata), berseem (Trifolium alexandrinum), chickpea (Cicer arietinum), lentil (Lens culinaris) and peanut (Arachis hypogaea)) was determined and isolates of each species having higher values were used for field experiments. Assay for root / shoot elongation, root colonization in plates were carried out under controlled conditions. The rhizosphere soil of wheat and rice were assayed for the Indole Acedic Acid (IAA) content 15 and 30 days after germination / transplanting, respectively. Results revealed that significant increase was observed in the yield parameters of wheat and rice. Highest wheat grains were produced i.e., 4917 kg ha-1 with Rhizobium sp of mungbean (Mb3) followed by 4823 with Rhizobium sp of berseem (Br3) than control i.e., 4500 kg ha-1. Similarly, the maximum paddy yield i.e., 4667 kg ha-1 with Rhizobium sp of mungbean (Mb3) followed by 4625 Rhizobium sp of berseem (Br3) inoculation was obtained as compared to control i.e., 4208 kg ha-1. Other physical parameters of wheat and rice also showed positive response to inoculation and have elevated levels of IAA in the rhizosphere of inoculated treatments. Results clearly demonstrated that Rhizobium species increased the yield of rice and wheat.