Abstract
One of the ways to increase the competitive survivability of rhizobial biofertilizers and thus achieve better plant growth under such conditions is by modifying the rhizospheric environment or community by addition of nonrhizobial nodule-associated bacteria (NAB) that cause better nodulation and plant growth when coinoculated with rhizobia. A study was performed to investigate the most commonly associated nodule-associated bacteria and the rhizospheric microorganisms associated with the Fenugreek (Trigonella foenum-graecum) plant. Isolation of nonrhizobial isolates from root nodules of Fenugreek was carried out along with the rhizospheric isolates. About 64.7% isolates obtained from Fenugreek nodules were gram-negative coccobacilli, 29.41% were gram-positive bacilli, and all rhizospheric isolates except one were gram-positive bacilli. All the isolates were characterized for their plant growth promoting (PGP) activities. Two of the NAB isolates M2N2c and B1N2b (Exiguobacterium sp.) showed maximum positive PGP features. Those NAB isolates when coinoculated with rhizobial strain—S. meliloti, showed plant growth promotion with respect to increase in plant's root and shoot length, chlorophyll content, nodulation efficiency, and nodule dry weight.
Highlights
Plant growth promoting rhizobacteria (PGPR) are a very small portion of the total rhizobacterial community [1]
One of the ways to increase the competitive survivability of rhizobial biofertilizers and achieve better plant growth under such conditions is by modifying the rhizospheric environment or community by addition of nonrhizobial nodule-associated bacteria (NAB) that cause better nodulation and plant growth when coinoculated with rhizobia
Root nodule associated bacteria were isolated from the nodules of Fenugreek plants from different field areas on the Yeast Extract Mannitol Agar (YEMA)/NA and rhizospheric isolates from the soil adhering to the roots of the plant were isolated on the Nutrient Agar (NA) medium
Summary
Plant growth promoting rhizobacteria (PGPR) are a very small portion (about 2–5%) of the total rhizobacterial community [1]. Such PGPR use one or more direct or indirect mechanisms to improve the growth and health of plants. These mechanisms can be active simultaneously or independently at different stages of plant growth. Among these are phosphate solubilization, biological nitrogen fixation, improvement of other plant nutrients uptake, and phytohormone production (like indole-3-acetic acid) are some of the regulators that profoundly influence plant growth [2]. PGPR have beneficial effects on legume growth and some
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