ANTAGONISME BACILLUS SP. TERHADAP PHYTOPHTHORA INFESTANS DAN IDENTIFIKASINYA BERDASARKAN SEKUENS GEN 16S RRNA DAN GYRB

UTAMI HANDAYANI, Dr. Tri Joko, S.P., M.Sc.

2014 | Skripsi | ILMU HAMA & PENYAKIT TUMBUHAN

Penyakit hawar daun kentang (late blight) yang disebabkan oleh Phytophthora infestans merupakan penyakit utama pada tanaman kentang. Penyakit hawar daun dapat menimbulkan kerugian dan kehilangan hasil hingga 100%. Bacillus sp. merupakan salah satu agens hayati yang mampu mengendalikan penyakit hawar daun kentang. Penelitian ini bertujuan untuk mengetahui keefektifan Bacillus sp. dalam menghambat pertumbuhan patogen Phytophthora infestans secara in vitro dan identifikasi Bacillus sp. secara molekuler berdasarkan sekuens gen 16S rRNA dan gyrB. Untuk mengetahui kemampuan bakteri dalam menghambat patogen dilakukan pengujian antagonis dan uji enzim. Pengujian antagonis yang dilakukan meliputi uji oposisi langsung, co-culture dan filtrat kultur. Uji kemampuan bakteri dalam menghasilkan enzim meliputi uji selulase, protease dan pencairan gelatin. Identifikasi bakteri secara molekuler dilakukan dengan analisis filogenetik sekuens bakteri berdasarkan gen 16S rRNA dan gyrB. Hasil penelitian menunjukkan bahwa Bacillus sp. mampu menekan pertumbuhan P. infestans secara in vitro baik pada uji oposisi langsung, co-culture maupun filtrat kultur. Bakteri Bacillus sp. mampu menghasilkan enzim selulase, protease dan gelatinase. Hasil analisis filogenetik berdasarkan sekuens gen 16S rRNA menunjukkan bahwa bakteri Bacillus sp. isolat TbPh7 tidak dapat dibedakan dengan spesies Bacillus spp. lainnya. Hasil analisis filogenetik berdasarkan sekuens gen gyrB menunjukkan bakteri Bacillus sp. isolat TbPh7 tergolong ke dalam spesies bakteri Bacillus amyloliquefaciens subsp. plantarum.

Potato leaf blight caused by Phytophthora infestans is the major disease on potato crops. The leaf blight disease can cause yield losses of up to 100%. Bacillus sp. is one of a biological agents which able to control leaf blight disease. The purpose of this study was to determine the effectiveness of Bacillus sp. to inhibit the growth of Phytophthora infestans in vitro and to identify Bacillus sp. based on 16S rRNA and gyrB gene sequences. The ability of Bacillus sp. to inhibit the pathogens, was tested by antagonists and enzyme tests. Testing was conducted on the antagonist test was direct opposition, co-culture and culture filtrate. Testing of ability the bacteria to produce enzymes was conducted by cellulase, protease and gelatin liquefaction test. The molecular identification of bacteria was carried by phylogenetic analysis based on 16S rRNA and gyrB gene sequences. The results showed that Bacillus sp. was able to suppress the growth of P. infestans as shown by in vitro test in direct opposition, co-culture and culture filtrate. The Bacillus sp. was able to produce cellulase, protease and gelatinase enzymes. The results of phylogenetic analysis based on 16S rRNA gene sequences showed that the Bacillus sp. TbPh7 isolate was indistinguishable to other Bacillus spp. The results of phylogenetic analysis based on gyrB gene sequences showed that Bacillus sp. TbPh7 isolate belong to Bacillus amyloliquefaciens subsp. plantarum.

Kata Kunci : Bacillus sp., P. infestans, antagonisme, 16S rRNA, gyrB.