Authors:Vidya R Sankar, Greeshma Thomas, E.M.Muralidharan
Abstract:In vitro shoot cultures of Dendrocalamus longispathus, a tropical sympodial bamboo were found to be harboring the endophytic Gram positive bacteria, Sporosarcina pasteruii, which offered protection against contamination from other microbes and permitted shoot multiplication and increase in shoot biomass. Establishment of axenic cultures by treating with gentamicin (250µg/ml) resulted in significant reduction in shoot multiplication rates and growth. Indole 3-Acetic Acid (IAA) biosynthesis by the endophyte, correlated to the improved growth and multiplication rate of the shoots, was revealed by lift membrane assay. The production of IAAwas eight times (98.76 µg/ml) in shoot cultures with the endophytes than that of the basal medium with the isolate alone (12.00 µg/ml). Growth promotion of in vitro shoot cultures by S. pasteruii was however limited to the host species and in shoot cultures of three non-host bamboo species viz. Bambusa balcooa, Pseudoxytenanthera ritcheyi and Dendrocalamus strictus. Production of siderophores by S. pasteruii was confirmed by CAS Blue agar test and an antagonistic effect against fungal and other bacterial contamination was demonstrated through dual culture. Detection and retention of potentially beneficial endophytes in tissue culture through the simple and rapid method employed can be a routine procedure to improve the efficiency of micropropagation in general.
Keywords:Endophytes, bamboo, micropropagation, Sporosarcina pasteurii, Bacillus pasteruii, plant growth promotion