Abstract

Aris Tri Wahyudi*, Rina Puji Astuti, Asri Widyawati, Anja Meryandini, and Abdjad Asih Nawangsih

Rhizobacteria of Bacillus species were isolated from the rhizosphere of soybean plant of Cirebon, Indonesia, and further examined for plant growth promoting activities. A total of 118 isolates identified as Bacillus sp., 90 isolates (76.3%) among them positively produced phytohormone indole acetic acid (IAA). The 12 isolates (13.3%) were selected, initially on the basis of germinating seed bioassay in which the root length, shoot length or number of lateral root of the seedling was enhanced significantly. All those 12 isolates produced siderophore and 11 isolates (91.7%) were able to solubilize phosphate. Furthermore, 3 isolates (25%) among them were able to inhibit the growth of Fusarium oxysporum, 9 isolates (75%) inhibited the growth of Rhizoctonia solani, and 1 isolate (8.3%) of Bacillus sp. inhibited the growth of Sclerotium rolfsii. DNA sequence analysis of 16S rRNA genes of those 12 isolates revealed that, all of them similar with Bacillus sp. cluster and was separately divided into four groups. This study has pointed out 12 isolates of Bacillus sp. that may be applicable as inoculants according to each supporting characters as growth promoter rhizobacteria.