Abstract
Diazotrophic endophytic bacteria contribute to the plant growth using various plant growth promoting traits as well as by inducing the plant defence mechanism upon pathogen attack. Aim of the present study was to isolate true diazotrophic endophytic bacteria from the total diazotrophic bacterial community of wheat and pearl-millet plants. Further, these isolates were evaluated for their potential of plant growth promotion by in vitro and in vivo experiments. We isolated total three diazotrophic endophytic bacteria based on their growth after repetitive subculturing on nitrogen free medium. Molecular characterization of all three isolates showed affiliation to the genera Agrobacterium, Pseudomonas and Brevundimonas. In vitro analysis of plant growth promoting traits showed positive result for indole acetic acid (IAA) production, cellulase and protease activity. The IAA production is found between the ranges of 98 to 113 µg ml-1. All the endophytic bacterial isolates showed the PCR amplification of NifH gene and ammonia production. Diazotrophic endophytic bacterial isolates (PR1, JB3 and JB6) were tested for their capacity to promote the plant growth using pot experiment. All the diazotrophic endophytic bacteria differ in their plant growth promotion ability as analyzed by various plant growth parameter compared to the untreated control plants. In Pot experiment, PR1 and JB6 showed a significant difference in dry weight of root, whereas JB3 and JB6 showed the significant differences in shoot length and total nitrogen content (p≤0.05) compared to the untreated plants.
Highlights
Soil is a rich source of a diverse group of bacterial communities and diversity of these bacteria get vary according to the environmental condition such as temperature, pH and altitude etc. (Gourmelon et al, 2016; Praeg et al, 2019)
Endophytic bacteria define as the microbes which once in their life cycle reside inside the internal tissues of the plants and can be re-isolated upon re-inoculation into the plant system known as a true endophyte (Reinhold-Hurek and Hurek 1998; Hardoim et al, 2015)
The pure culture of the diazotrophic endophytic bacteria was selected by plating the culture on nitrogen free base (NFb) medium
Summary
Soil is a rich source of a diverse group of bacterial communities and diversity of these bacteria get vary according to the environmental condition such as temperature, pH and altitude etc. (Gourmelon et al, 2016; Praeg et al, 2019). Diazotrophic bacteria have been reported from rice (Ladha and Barraquio 1997; Gyaneshwar et al, 2001; Prakamhang et al, 2009; Ji et al, 2014; Patel and Archana 2017), maize (Baldani et al, 1986; Estrada et al, 2002; Patel and Archana 2017), wheat (Silveira et al, 2016; Patel and Archana 2017), sorghum (Mareque et al, 2015; Patel and Archana 2017) and pearl millet (Patel and Archana 2017) These studies indicate the nitrogen fixation is limited to the legumerhizobia but it associated with cereal plants. This knowledge was utilized to study its ability to promote the plant growth promotion under in vivo condition
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