Plant growth promotion using microbial IAA producers in conjunction with azolla: a novel approach

Abstract

Studies were conducted to find efficient Indole acetic acid producing strains and assessing the effectiveness of combined dose of azolla (dried) and IAA producers on plant growth. Out of ten isolates, only two isolates, viz, F1 and G2 were found to be potent IAA producers and were used for further experiments. It was found that the isolate F1 and G2 produced maximum amount of IAA at 0.9% tryptophan and incubation for 72 h at room temperature. The optimum pH for IAA production for isolates F1 and G2 was found to be at pH 9. The isolates were also assessed for the presence of other plant growth promoting activity, such as hydrogen cyanide production, oxalate solubilization, phosphate solubilization and zinc solubilization. Effect of IAA producers on seed germination was done by pot experiments carried out into sets. Isolates F1 and G2 were found efficient for plant growth promotion in desired aspects. Effect of combined dose of azolla and IAA producers on seed germination was assessed by pot experiments. For this, dried powder of azolla was added during sowing of culture treated seeds. No further culture supply was given to the seeds. Azolla has high protein content. Slow protein releasing property of azolla can be useful to provide constant supply of the precursor (tryptophan) for IAA synthesis by isolate. In addition to the plant exudates, azolla may also give constant supply of tryptophan. From all the assessed samples, the isolates FI and G2 showed efficient growth of plants in all aspects. G2 was found to be more potent than F1. So as to assess the compatibility of isolate in natural conditions, field studies were done. Four plots designed having individual size 9 × 5 m, were used. It was found that plots 3 (only culture) and 4 (culture with azolla) showed better plant growth as compared to others. On the basis of IAA producing ability of G2, pot experiments and field studies, it was concluded that isolate G2 can be used alone or in conjunction with azolla as a biofertilizer to get better plant growth.

Screening and optimization of indole-3-acetic acid production and phosphate solubilization by rhizobacterial strains isolated from Acacia cyanophylla root nodules and their effects on its plant growth

“…produced more IAA at pH 9, but this production decreased with the pH decrease. Similarly, previous studies showed that the maximum yield of IAA was obtained at pH 9 [14,45]. Other authors found that the maximum amount of IAA was produced at neutral to slightly alkaline pH [37,46,47].…”

Plant Growth Promoting Effects of Nepalese Sweet Potato Endophytes

“…Earlier reports have shown that plant-associated bacteria can improve plant growth by IAA production [10,[21][22][23] and nitrogen fixation [8]. In this study, bacterial inoculation also showed positive effects on the growth of sweet potato.…”

Field Based Assessment of Capsicum annuum Performance with Inoculation of Rhizobacterial Consortia

“…The highest level, 78.7 µg/mL, was produced by isolate Bacillus pumilus followed by Bacillus subtilis (72.0 µg/mL) when the media was supplemented with 500 µg/mL of l -tryptophan. It was investigated that IAA is the most important plant hormone produced by rhizobacterial strains which is directly involved in plant growth promotion [15]. The production of siderophores, low molecular weight iron chelating compounds, was detected in both isolates, conferring them a competitive merit to biocontrol agents.…”