Assessing the Plant Growth-promoting Traits and Host Specificity of Endophytic Bacteria of Pulse Crops

Background: Symbiotic associations between legumes and Rhizobia are ancient and fundamental. However, the plant growthpromoting endophytes other than Rhizobia are not yet fully explored for pulses productivity. The present study was aimed to isolate efficient endophytic bacteria from pulses, assess their diversity, screen their plant growth -promoting activities and to test their potential as bio inoculants for pulses. Methods: We have isolated several endophytic bacteria from pulse crops more specifically from blackgram (Vigna mungo) and greengram (Vigna radiata). After careful screening, 15 promising endophytic isolates were selected for this study. The identification of endophytic bacterial isolates was performed by 16S rRNA gene sequencing. The isolates were tested for their potential for the plant growth -promoting traits such as nitrogen fixation, phosphate solubilization, indole-3-acetic acid production, siderophore secretion and antifungal activity. Pot culture experiments were conducted with the screened potential endophytic cultures. Result: The 16S rRNA gene sequencing revealed that species of Enterobacter, Bacillus, Pantoea, Pseudomonas, Acromobacter, Ocrobacterium were found as endophytes in blackgram and greengram. The in vitro screening identified Bacillus pumilus (BG-E6), Pseudomonas fluorescens (BG-E5) and Bacillus licheniformis (BG-E3) from blackgram and Pseudomonas chlororaphis (GG-E2) and Bacillus thuringiensis (GG-E7) from greengram as potential plant growth -promoting endophytes. These strains showed antagonism against plant pathogenic fungi. Upon inoculation of these endophytic PGPR strains, the blackgram and greengram growth and yield got increased. Among the strains, BG-E6 recorded 14.7% increased yield in blackgram and GG-E2 accounted for a 19.5% yield increase in greengram compared to respective uninoculated control. The experimental results showed that there was a host specificity found among the endophytic bacterial cultures with pulses. The cross inoculation of endophytic strains did not perform well to enhance the growth and yield of their alternate hosts.