Influence of Plant Growth Promoting Rhizobium on Growth of Pigeon Pea [ Cajanus cajan (L.) Millsp.]

Background: Symbiotic nitrogen fixation plays a major role in the production of million tons of total biological nitrogen. The Rhizobium not only fixes the nitrogen but also produces plant growth promoting hormones. In this view, the present study was undertaken to characterize the native Rhizobium isolates for their functional properties and evaluate on pigeon pea for their plant growth promotional activities. Methods: The present investigation was carried out during the year 2018-19 at UAS, Dharwad. Five of the native isolates obtained from Northern district of Karnataka were subjected for functional characterization using standard methods. The isolates were also tested for their plant growth promotional activities. Result: The IAA production in the isolates was ranged from 20.50 to 22.85 mu g IAA/ml of broth and GA production from 13.40 to 14.51 mu g/25 ml of broth. ACC deamination activity in the isolates was ranged from 57.50 to 75.5 nmoles of alpha-ketobutyrate/mg/h of broth. All the isolates exhibited their ability to solubilize P and Zn. Out of ten isolates, four isolates exhibited potential to inhibit mycelial growth of Fusarium oxysporum f. sp. udum and per cent inhibition was ranged from 48.75 to 73.75. All the isolates were found to be positive for siderophore and HCN production. The isolate AMVPR98 performed better with respect to all the growth parameters of pigeon pea. Molecular characterization of isolate AMVPR98 revealed 99% similarity with Rhizobium pusense strain AB3.