Selection of Rhizobacteria Indole Acetic acid Producing and Its tests on White Albizia (Paraserianthes falcataria L. Nielsen)

Abstract

Rhizobacteria is a bacteria that colonize plant roots and have a potency as a plant growth promotor. Plant growth promoting substances produced by rhizobacteria viz indole acetic acid (IAA), cytokinin, giberalin, and ethylene. IAA plays an important role in plant growth. Research about rhizobacteria effect on forest plant growth is needed to obtain rhizobacteria strains that have a potency for producing the optimal IAA. Therefore, the objectives of this research were to select rhizobacteria that produced indole acetic acid that derived from the legume plant rhizosphere and tested its effect on plant growth of white albizia (Paraserianthes falcataria L. Nielsen). Based on colorimetric assay, there were three isolates that produce high amount of IAA, ie L6.5, L8.2, and L9.1. The results of five treatments on germination of Paraserianthes falcataria L. Nielsen gave no effect of the main root length, average of lateral root length, root dry weight, and shoot dry weight. Treatment of rhizobacteria strain L8.2 supplemented with 1,0 mM tryptophan produced the highest effect on the average number of lateral roots and leaves. The results of bacterial identification by using MicrobactTM 12A+12B ID System or API® 20 NE kit showed that strain L6.5, L8.2, or L9.1 belonging to Burkholderia cepacia.

Rizobakteria merupakan bakteri yang berkoloni di perakaran tanaman dan berpotensi sebagai pemacu pertumbuhan tanaman. Zat pengatur tumbuh yang dihasilkan oleh rizobakteria antara lain indole acetic acid (IAA), sitokinin, giberalin, dan etilen. IAA berperan penting dalam pertumbuhan tanaman. Penelitian mengenai pengaruh rizobakteria pada pertumbuhan tanaman hutan perlu dilakukan untuk memperoleh galur rizobakteria yang berpotensi menghasilkan IAA optimal. Tujuan penelitian ini untuk menyeleksi rizobakteria penghasil asam indol asetat yang berasal dari rizosfer tanaman legum dan melihat pengaruhnya terhadap pertumbuhan tanaman sengon (Paraserianthes falcataria L. Nielsen). Berdasarkan uji kolorimetri terdapat tiga isolat penghasil IAA yang tinggi, yaitu galur L6.5, L8.2, dan L9.1. Hasil uji lima perlakuan pada tanaman sengon menunjukkan pengaruh yang tidak berbeda nyata terhadap parameter panjang akar utama, rata-rata panjang akar lateral, bobot kering akar, dan bobot kering batang. Perlakuan rizobakteria galur L8.2 yang ditambahkan 1,0 mM triptofan menghasilkan pengaruh tertinggi pada rata-rata jumlah akar lateral dan daun. Hasil identifikasi bakteri menggunakan kit MicrobactTM 12A+12B ID System atau API® 20 NE menunjukkan bahwa galur L6.5, L8.2, dan L9.1 termasuk Burkholderia cepacia.