Pengaruh Sumber Isolat Rizobakteri Terhadap Efektifitas Daya Hambat Pertumbuhan Koloni Patogen Colletotrichum spp. Penyebab Penyakit Antraknosa Pada Tanaman Cabai Merah (Capsicum annuum L.) Secara In Vitro The Effect of Rhizobacteria Isolate Sources on the Effectiveness of Inhibitory Power of Colletotrichum spp. Causes of Anthracnose Disease in Chili Plants (Capcisum annuum L.) In Vitro Zuhramita1, Syamsuddin2, Halimursyadah2 1Mahasiswa Jurusan Agroteknologi, Fakultas Pertanian, Universitas Syiah Kuala 2Staf Dosen Jurusan Agroteknologi, Fakultas Pertanian, Universitas Syiah Kuala Abstrak. Penelitian ini bertujuan untuk mendapatkan sumber isolat rizobakteri yang berpotensi sebagai daya hambat pertumbuhan koloni patogen Colletotrichum spp. penyebab penyakit antraknosa pada tanaman cabai merah secara in vitro. Penelitian dilaksanakan di Laboratorium Ilmu dan Teknologi benih Jurusan Agroteknologi, Fakultas Pertanian, Universitas Syiah Kuala, Darussalam Banda Aceh. Pelaksanaan penelitian berlangsung pada bulan Februari sampai Juni 2020. Penelitian ini menggunakan Rancangan Acak Lengkap (RAL) Non Faktorial. Faktor yang diteliti adalah 28 isolat rizobakteri dari sumber pengambilan yang berbeda yaitu, 13 isolat dari Lembah Seulawah dan 15 isolat dari desa Ladong yang di ulang sebanyak 3 kali. Rizobakteri yang digunakan merupakan hasil dari uji potensi awal yang berpotensi sebagai kandidat agens biokontrol dalam menghambat petumbuhan koloni patogen Colletotrichum spp. secara in vitro. Parameter yang diamati yaitu persentase penghambatan pertumbuhan koloni patogen Colletotrichum spp, laju penghambatan pertumbuhan koloni patogen Colletotrichum spp, dan karakteristik morfologi rizobakteri agens biokontrol. Hasil penelitian menunjukkan bahwa 28 isolat rizobakteri memiliki kemampuan dalam menekan pertumbuhan koloni patogen Colletotrichum spp. Isolat LS 4/4 dan LS 4/1 memiliki daya hambat yang baik dengan persentase penghambatan 75,06% yang tergolong kategori aktivitas sangat tinggi (++++ = ≥ 75% DH) dan 70,22% tergolong kategori aktivitas tinggi (+++ = 61-75% DH) dalam menekan pertumbuhan patogen Colletotrichum spp. secara in vitro. Isolat LS 4/4 memiliki memiliki ciri-ciri bentuk permukaan koloni datar, berwarna coklat muda dan bentuk pinggiran koloni tidak rata. Isolat LS 4/1 memiliki ciri-ciri bentuk permukaan koloni cembung, berwarna coklat muda dan bentuk pinggiran koloni tidak rata. Pada laju penghambatan pertumbuhan koloni rizobakteri terhadap patogen, Isolat rizobakteri LS 5/3 dan LS 5/2 memiliki laju penghambatan terhadap pertumbuhan patogen Colletotrichum spp. yang baik dengan nilai rata-rata 3,54 mm hari-1 dan 3,28 mm hari-1. Isolat ini memiliki ciri-ciri bentuk permukaan koloni datar, berwarna coklat dan bentuk pinggiran koloni tidak rata. Kata kunci : Antraknosa, karakteristik, patogen, rizobakteri Abstract. This study aims to obtain a source of rhizobacterial isolates that have the potential to inhibit the growth of the pathogenic colony Colletotrichum spp. the cause of anthracnose disease in red chili plants in vitro. The research was conducted at the Laboratory of Seed Science and Technology, Department of Agrotechnology, Faculty of Agriculture, Syiah Kuala University, Darussalam Banda Aceh. The research was carried out from February to June 2020. This study used a non-factorial completely randomized design (CRD). The factors studied were 28 isolates of rhizobacteria from different sources, 13 isolates from the Seulawah Valley and 15 isolates from Ladong Village which were repeated 3 times. The rhizobacteria used are the results of the initial potential test which are potential candidates for biocontrol agents in inhibiting the growth of the pathogenic colony of Colletotrichum spp. invitro. The parameters observed were the percentage inhibition of the growth of thePathogenic colony Colletotrichum spp., the rate of inhibition of the growth of the Colletotrichum spp. And the morphological characteristics of the biocontrol agent rhizobacteria. The results showed that 28 rhizobacterial isolates had the ability to suppress the growth of pathogenic colonies Colletotrichum spp. LS 4/4 and LS 4/1 isolates had good inhibition with an inhibition percentage of 75.06% which was classified as a very high activity category (++++ = ≥ 75% DH) and 70.22% belonging to the high activity category (+ ++ = 61-75% DH) in suppressing the growth of the pathogen Colletotrichum spp. in vitro.Isolate LS 4/4 has the characteristics of flat colony surface shape, light brown color and uneven colony periphery shape. Isolate LS 4/1 was characterized by a convex colony surface, light brown color and uneven colony margins. At the rate of inhibition of growth of rhizobacterial colonies against pathogens, LS 5/3 and LS 5/2 rhizobacterial isolates had an inhibition rate against the growth of the pathogenic Colletotrichum spp. good with an average value of 3.54 mm day-1 and 3.28 mm day-1. This isolate has the characteristics of flat colony surface shape, brown color and uneven colony periphery shape. Key words: Anthracnose, characteristics, pathogens, rhizobacteria