Abstract
Endophytic bacteria colonizing the internal tissues of plants are known to improve plant growth by a wide variety of mechanisms. This study envisages the isolation and evaluation of plant growth promoting attributes of bacterial endophytes in perennial fern Ophioglossum reticulatum L. A total of 20 phenotypically distinguishable bacterial endophytes were isolated from surface sterilized leaf lamina, petiole, rhizome and spike of O. reticulatum L. The Shannon-Weaver diversity index showed that the rhizome (1.54) harbor more diverse types of endophytic bacteria than in its petiole, leaf lamina and spike. The isolated endophytes were characterized on the basis of micromorphological and physio-biochemical characters and tentatively assigned to the genus Bacillus, Pseudomonas and Staphylococcus. The isolates showed distinct variations in their enzymatic activities, sugar fermentation and antibiotic sensitivity profile. A number of endophytic isolates showed plant growth promoting activities like production of indole-3-acetic acid (IAA) and siderophore, growth in nitrogen-free medium and solubilization of phosphate. Time course of growth and IAA production by the potent isolate Bacillus OPR 7 have been determined. Exploitation of such plant growth promoting endophytes appears to be one of the best options in increasing biomass yield and improving plant fitness and productivity.
Highlights
All plants in nature harbor a diverse community of endophytic bacteria that colonize the internal tissues of the plant without imposing any negative impact on their host [1]
Surface sterilized segments of leaf lamina, petiole, rhizome and spike of Ophioglossum reticulatum L. incubated on tryptic soy agar, glycerol asparagine agar and R2A agar plates showed growth of morphologically distinguishable bacterial colonies surrounding the segments after 48–96 h of incubation at 32 °C (Figure 1)
A total of 20 phenotypically distinguishable bacterial endophytes were isolated in pure form from 497 segments (202 leaf lamina, 60 petiole, 179 rhizome and 56 spike) of O. reticulatum L
Summary
All plants in nature harbor a diverse community of endophytic bacteria that colonize the internal tissues of the plant without imposing any negative impact on their host [1]. They have been isolated from roots, leaves, stems, flowers, fruits, and seeds from various plants [2] and found to play a pivotal role in plant growth enhancement. Such endophytic bacteria with plant growth promoting characters have been reported from different plants [5,6] These include species of Pseudomonas, Azospirillum, Azotobacter, Klebsiella, Alcaligenes, Arthrobacter, Burkholderia, Bacillus and Serratia [7]. Planococcus sp., Micrococcus sp., Bacillus sp., Methylococcus sp., Acinetobacter sp. and Acetobacter sp. endophytic to Rosa damascena trigintipeta were found to produce indole-3-acetic acid (IAA), solubilize calcium phosphate and produce siderophore [12]
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