Indole-3-acetic acid of rhizobacteria isolated from Imperata cylindrica grasslands in Indonesia

Indole-3-acetic acid (IAA) producing bacteria is a group of bacteria that capable of improving crop's root competence regarding getting nutrients, ions, and water and initiate good conditions to support crops growth in Imperata grasslands. This study aims to screen and identify IAA-producing bacteria from Cibinong, Katingan, and East Nusa Tenggara, Indonesia. Sixty-eight of IAA-producing bacteria obtained from the previous study are identified based on the 16S rRNA gene and qualitatively and quantitatively screened after a year of preservation in 10% glycerol at -80°C. The finding of this study highlighted that there are 14 genera of IAA-producing bacteria obtained Rhizobium, Pseudomonas, Klebsiella, Pantoea, Paraburkholderia, Acinetobacter, Enterobacter, and Serratia (Phylum Proteobacteria); Bacillus (Phylum Firmicutes); Microbacterium, Arthrobacter and Leifsonia (Phylum Actinobacteria); and Chryseobacterium and Pedobacter (Phylum Bacteroidetes). However, only seven genera (39 isolates) are quantitatively measured for IAA production until 72 h of incubation. The range of IAA production in several genera until 72 h of incubation for Rhizobium, Chryseobacterium, Pseudomonas, Bacillus, Klebsiella, Enterobacter and Serratia genus are 5.55-11.97 mg ml−1, 16.83 mg ml−1, 0.88-21.67 mg ml-1, 1.94-6.16 mg ml−1, 9.42-179.57 mg ml−1, 3.31-48.89 mg ml-1, and 18.59 mg ml−1 respectively. This preliminary study showed that IAA production by bacteria was still increasing until 72 h of incubation. Strain KAT-229 was identified as Klebsiella sp. showed the highest level of IAA production (179.57 mg ml−1) than other isolates when strains on the stationary growth phase in the presence of L-Trp. This study clearly shows that the isolates could be potentially used for revegetating of degraded land of Imperata grasslands. Further studies are required to achieve incubation time for the highest IAA production.