Isolation and screening of IAA producing bacteria and their potential in promoting plant growth

Abstract

Recent studies have highlighted the effect of the phytohormone synthesised by PGPR on plant growth, in particular IAA. The current study focuses on the isolation of IAA-producing rhizobacteria and the verification of their potential to promote wheat growth. From 61 IAA-producing bacteria, four isolates were selected. The influence of temperature, pH and concentration of L-tryptophan on IAA production were verified. The selected isolates were also tested for their ability to promote wheat germination and growth. The parameters: shoots and roots length, fresh and dry weight of shoots and roots as well as chlorophyll content were measured. The results indicated that optimal conditions for IAA production were observed at different temperatures: 30°C for isolate O3 (120 ?g/ml) and 35°C for isolates F4 and P17 (120 ?g/ml and 105 ?g/ml respectively). The pH conditions favoring production were pH 7and 8 and the concentration of L-tryptophan was 800 ?g/ml and 650 ?g/ml. Wheat growth parameters were significantly enhanced with bacterial treatment compared to the control. All the selected isolates enhance significantly shoot growth but not root growth, suggesting they may be specific strains for promoting stem elongation. In addition, chlorophyll content was significantly higher in the treated wheat than in the control.