Eksplorasi Rizobakteri Indigenous dan Karakterisasi secara Fisiologis serta Uji In Vitro terhadap Daya Hambat Patogen Rigidoporus microporus pada Tanaman Pala (Myristica fragrans) The Exploration of Indigenous Rhizobacteria and Physiological Characterization and In Vitro Test of Rigidoporus microporus Pathogenic Inhibition Rate on Nutmeg (Myristica fragrans) Abstrak. Penelitian ini untuk mengetahui pengaruh jenis rizobakteri Indigeneus yang berpotensi sebagai agen biokontrol dan RPPT terhadap daya hambat patogen Rigidoporus microporus pada tanaman pala secara in vitro. Penelitian ini dilaksanakan di Laboratorium Ilmu dan Teknologi Benih Jurusan Agroteknologi, Fakultas Pertanian, Universitas Syiah Kuala, Darussalam Banda Aceh. Pelaksanaan penelitian dimulai dari Februari sampai Mei 2019. Penelitian ini dilakukan dengan menggunakan Rancangan Acak Lengkap (RAL) non faktorial. Faktor yang diteliti dalam penelitian ini adalah Eksplorasi Rizobakteri Indigeneus dan Karakterisasi secara Fisiologis serta Uji In Vitro terhadap Daya Hambat Patogen Rigidoporus microporus pada Tanaman Pala yang terdiri dari 18 isolat rizobakteri dengan 3 kali ulangan, dilanjutkan dengan uji Duncan Multiple Range Test (DMRT) pada taraf 5%. Parameter yang diamati adalah persentase daya hambat pertumbuhan koloni patogen, laju penghambatan pertumbuhan koloni patogen, Uji gram, Kemampuan Agens Memproduksi Hidrogensianida (HCN), kemampuan dalam melarutkan fosfat, dan kemampuan memproduksi asam indol asetat (IAA). Hasil penelitian ini menunjukkan bahwa hasil analisis ragam (Uji F) menunjukkan bahwa perlakuan isolat rizobakteri berpengaruh nyata dalam menghambat pertumbuhan koloni cendawan patogen Rigidoporus microporus. Adapun rata-rata presentase (%) dari 18 isolat rizobakteri memiliki daya hambat dengan aktivitas yang rendah, (< 50%). Dari laju penghambatan tidak berbeda nyata terhadap pertumbuhan koloni patogen dengan laju penghambatan tingkat tertinggi yaitu pada AP 8/2 sebesar 4,13 mm/hari sedangkan AP 5/8 dan AP 7/4 memiliki tingkat rendah yaitu 2,82 mm/hari. Hasil pengujian HCN Dari 18 isolat rizobakteri, 7 isolat rizobakteri yang dapat menghasilkan senyawa HCN. Satu isolat AP 8/2 diantaranya menghasilkan HCN dalam jumlah yang rendah, enam isolat menghasilkan HCN dalam jumlah yang sangat tinggi yaitu AP 4/5, AP 5/7, AP 6/1, AP 7/2, AP 7/3, AP 7/4, sedangkan 11 isolat lainnya tidak mampu menghasilkan senyawa HCN. Berdasarkan hasil pengamatan karakterisasi isolat rizobakteri agen biokontrol pada uji gram memiliki kesamaan dengan bakteri Bacillus sp. Isolat rizobakteri yang telah diuji dengan zat pewarna tandingannya berupa zat warna safranin dan lugol, rizobakteri akan bereaksi dengan gram positif dan gram negatif, dari 18 isolat rizobakteri yang termasuk dalam gram postitif yaitu AP 3/1, AP 3/10, AP 4/1, AP 4/5, AP 5/5, AP 5/6, AP 5/7, AP 5/8, AP 6/1, AP 7/2, AP 7/4, AP 7/5, AP 7/6, AP 8/2, sedangkan isolat rizobakteri yang termasuk dalam gram negatif yaitu AP 3/11, AP 5/3, AP 7/1, AP 7/3. Adapun isolat rizobakteri yang mampu dalam melarutkan fosfat yaitu ada 14 isolat, sedangkan sebanyak 4 isolat rizobakteri termasuk yang tidak mampu melarutkan fosfat yaitu AP 4/5, AP 5/6, AP 7/5, dan AP 8/2. Adapun Rerata yang tertinggi terdapat pada isolat rizobakteri AP 5/6 dengan memproduksi IAA yaitu 1,250 µg/ ml filtrat, sedangkan di isolat rizobakteri dengan tingkatan yang terendah terdapat pada isolat rizobakteri AP 3/1 yaitu 0,407 µg/ ml filtrat. Kata kunci : Pala, rizobakteri, patogen, daya hambat, Rigidoporus microporus. Abstract. This study was conducted to determine the effects of Indigenous Rhizobacteria which are potential to become biocontrol agents and Plant Growth Promoting Rhizobacteria by the in vitro inhibition of Rigidoporus microporus pathogens in Nutmeg (Myristica fragrans). This research was conducted at the Seed Science and Technology Laboratory of the Agrotechnology Department, Faculty of Agriculture, Syiah Kuala University, Banda Aceh. The research was conducted from February to May 2019. The research was conducted by using a non factorial Complete Randomized Design (CRD). The observed factors in this study were the indigenous rhizobacteria exploration and physiological characterization and the In vitro test on the inhibition of Rigidoporus microporus pathogen in Nutmeg which consisted of 18 rhizobacteria isolates within 3 replications, followed by Duncan Multiple Range Test (DMRT) at the level of 5%. The parameters observed were the inhibition percentage, the pathogenic colonies growth inhibition rate, gram test, the ability of agents to produce hydrogensanide (HCN), the ability to dissolve phosphate, and the ability to produce Indole Acetic Acid (IAA).From the analysis of covariance results (F Test) indicates that the rhizobacteria isolates treatment had a significant effect in inhibiting the colonies of the Rigidoporus microporus growth. The average percentage (%) of 18 rhizobacteria isolates inhibiting activity was low (< 50%). The inhibition rate was not significantly different from the pathogenic colonies growth, with the highest inhibitory rate was AP 8/2 of 4.13 mm /day and the lowest were AP 5/8 and AP 7/4 had a low level of 2.82 mm / day. HCN test results indicate that 7 of 18 rhizobacteria isolates could produce HCN compounds. The AP 8/2 isolates indicated with low amount of HCN production. The remaining 6 isolates produced HCN in a very high number namely AP 4/5, AP 5/7, AP 6/1, AP 7/2, AP 7/3, AP 7/4, while 11 remaining isolates were unable to produce HCN compounds.According to the observations of the rhizobacteria isolates of biocontrol agents characterization by gram test, that of similiar to the Bacillus sp. Rhizobacteria isolates that have been tested with counterparts in the form of safranin and lugol dyes, which rhizobacteria would react to the positive gram and negative gram. Among 18 rizobacteria isolates, those which included to be positive gram, namely AP 3/1, AP 3/10, AP 4/1 , AP 4/5, AP 5/5, AP 5/6, AP 5/7, AP 5/8, AP 6/1, AP 7/2, AP 7/4, AP 7/5, AP 7/6 , AP 8/2, while rizobacteria isolates included to be negative gram were AP 3/11, AP 5/3, AP 7/1, AP 7/3. There were 14 rhizobacteria isolates that were able to dissolve phosphate, while others 4 isolates were unable to dissolve phosphate namely AP 4/5, AP 5/6, AP 7/5, and AP 8/2. The highest average number of IAA producing was found in AP 5/6 rhizobacteria isolate as much as 1,250 µg / ml filtrate, while the lowest level of IAA was found in AP 3/1 rhizobacteria isolates, as much as 0.407 µg / ml filtrate. Keywords :Nutmeg, rhizobacteria, pathogen, inhibitory rate, Rigidoporus microporus