Antifungal and Phytohormone Production Potential of Azotobacter Chroococcum Isolates from Groundnut (Arachis Hypogea L.) rhizosphere and their Effect on Nodulation and dry Mass, alongwith Native Rhizobia in Pot Culture Experiment

Azotobacter chroococcum isolates from the rhizosphere of groundnut varieties from different localities were tested for their ability to produce antifungal metabolites and phytohormones - indol acetic acid (IAA) and gibberellins (GA). Out of the 25 isolates, KG 2, KG 3 and KG 5 were found to be more significant as compared with others. KG 2 exhibited activity against Aspergillus flavus, Aspergillus terrus and Fusarium oxysporum and produced indol acetic acid and gibberellins in 55 mu g /ml and 50 mu g /ml amount respectively; KG 3 exhibited activity against Aspergillus flavus and Aspergillus terrus and produced IAA and GA in 56 mu g /ml and 58 fig /ml amount respectively whereas KG 5 exhibited activity against Aspergillus terrus, Alternaria alternata and Fusarium oxysporum and produced IAA and GA in 53 mu g/ml and 62 mu g/ml amount respectively. A study on the effect of mixed culture inoculation of these three isolates of Azotobacter chroococcum and native isolates of Rhizobia on nodulation and dry mass of groundnut (Arachis hypogea L.) var. TPG 41, JL 286 and JL 501 was undertaken in pot culture experiment by using randomized block design. A significant increase in nodulation and dry mass of each variety was observed due to mixed culture inoculation over uninoculated control. Treatment with Azotobacter alone or Rhizobium alone and with mixture of Azotobacter and Rhizobium biofertilizers also increased nodulation and thy mass over control but it was less than the native species. Therefore, these isolates could be used as bifertilizers and biocontrol agents.