Potensi Bacillus subtilis subsp. subtilis RJ09 sebagai Agens Pengendali Hayati Penyakit Bercak Daun Cengkih

Potensi Bacillus subtilis subsp. subtilis RJ09 sebagai Agens Pengendali Hayati Penyakit Bercak Daun Cengkih Cengkih merupakan tanaman asli Indonesia yang menjadi salah satu komoditas utama sektor perkebunan. Penyakit bercak daun berupa nekrosis sering ditemukan pada tanaman cengkih. Gangguan terhadap fotosintesis yang disebabkan oleh penyakit bercak daun dapat menyebabkan kematian pada tanaman. Bacillus diketahui dapat menghambat perkembangan patogen melalui mekanisme persaingan nutrisi dan antibiosis. Penelitian ini bertujuan mengidentifikasi Bacillus sp. RJ09 secara molekuler dan mengetahui potensinya dalam menekan perkembangan Pestalotiopsis sp., penyebab bercak daun tanaman cengkih secara in vitro. Identifikasi cendawan dilakukan dengan mengamati morfologi yang meliputi warna koloni, bentuk, dan ukuran konidium cendawan hasil isolasi. Identifikasi Bacillus sp. RJ09 dilakukan dengan polymerase chain reaction (PCR) menggunakan sepasang primer yang mengamplifikasi wilayah gen gyrB sebesar ±1400 pasang basa (pb) yang dilanjutkan dengan analisis sikuen. Pengujian kemampuan Bacillus sp. RJ09 sebagai agens hayati terhadap cendawan yang berasosiasi dengan bercak daun dilakukan dengan metode kultur ganda in vitro. Hasil identifikasi cendawan bercak daun tanaman cengkih diperoleh Pestalotiopsis sp. yang dapat menyebabkan bercak nekrosis berwarna kehitaman pada daun. Hasil identifikasi molekuler Bacillus sp. RJ09 menunjukkan nilai kemiripan tertinggi 99.40% dengan B. subtilis subsp. subtilis. Pengujian in vitro menunjukkan B. subtilis subsp. subtilis RJ09 dapat menghambat pertumbuhan koloni Pestalotiopsis sp. sebesar 75%.Cloves is one of the main plantation commodities and is native to Indonesia. Leaf spot disease with necrosis symptom is often found in clove plants. Interferences to photosynthesis caused by leaf spot disease can cause plant death. Bacillus is known to inhibit the development of pathogens through nutrient competition and antibiosis mechanism. This study aims to identify Bacillus sp. RJ09 through molecular approach and determine its potential in suppressing the development of Pestalotiopsis sp., the cause of clove leaf spot by in vitro examination. Identification of the fungus was carried out by observing the morphology which included the color of the colony, the shape and size of the conidium of the isolated fungus. Identification of Bacillus sp. RJ09 was performed by polymerase chain reaction (PCR) using a pair of primers that amplified gyrB gene region of ±1400 bp, followed by sequence analysis. The ability of Bacillus sp. RJ09 as a biological agent against fungi associated with leaf spot was determined using an in vitro double culture method. Pestalotiopsis sp. was found as the fungus associated with leaf spot disease and can cause black necrotic spots on the leaves. Molecular identification of Bacillus sp. RJ09 showed the highest similarity value of 99.40% with B. subtilis subsp. subtitles. In vitro dual culture showed B. subtilis subsp. subtilis RJ09 can inhibit the growth of Pestalotiopsis sp. colonies by 75%