Electronic Theses and Dissertation

Padi (Oryza sativa L.) merupakan tanaman pangan utama di Indonesia, namun sangat rentan terhadap serangan organisme pengganggu tanaman (OPT) seperti cendawan dan bakteri, yang dapat menurunkan produksi secara signifikan. Penyakit utama padi meliputi penyakit blas yang disebabkan Pyricularia oryzae, bercak daun coklat oleh Bipolaris oryzae dan hawar daun bakteri (HDB) yang disebabkan Xanthomonas oryzae pv. oryzae (Xoo). Aplikasi pestisida sintetis untuk pengendalian penyakit adalah praktik umum yang dilakukan, namun berdampak buruk bagi lingkungan. Oleh karena itu, diperlukan alternatif pengendalian yang lebih ramah lingkungan, seperti penggunaan bakteri endofit, Bacillus cereus dilaporkan berpotensi sebagai agens pengendali hayati patogen tanaman. Penelitian ini bertujuan untuk menguji potensi B. cereus asal tanaman padi dalam menekan beberapa patogen tanaman padi melalui percobaan in vitro dan in vivo.
Penelitian ini dilaksanakan di Laboratorium Ilmu Penyakit Tumbuhan dan Rumah Kasa Fakultas Pertanian Universitas Syiah Kuala. Penelitian ini terdiri atas 2 tahap percobaan yaitu in vitro dan in vivo. Pada percobaan in vitro, dilakukan uji antagonisme B. cereus terhadap patogen P. oryzae, B. oryzae dan Xoo. Proses ini melibatkan perbanyakan biakan B. cereus, P. oryzae, B. oryzae dan Xoo, diikuti dengan uji antagonisme B. cereus terhadap ketiga patogen tersebut. Parameter yang diamati adalah persentase daya hambat B. cereus terhadap patogen padi. Pada percobaan in vivo, ketahanan padi diinduksi menggunakan B. cereus, dengan merendam benih dan akar padi dalam suspensi B. cereus 109 sel/ml. Parameter yang diamati meliputi persentase benih berkecambah, masa inkubasi dan persentase keparahan penyakit.
Berdasarkan hasil penelitian, daya hambat tertinggi terhadap P. oryzae, B. oryzae dan Xoo masing-masing sebesar 79,16%, 68,21%, dan 64,44%. Persentase benih berkecambah, benih dengan perendaman suspensi B. cereus lebih unggul yaitu 89%. Masa inkubasi terlama masing-masing patogen adalah 12,33 hari untuk P. oryzae, 12,16 hari untuk B. oryzae, dan 10,33 hari untuk Xoo. Gejala awal pada P. oryzae muncul nekrosis berbentuk oval dan bagian tengah lebih terang, pada B. oryzae ditandai dengan munculnya bintik-bintik cokelat tua dan pada Xoo ditandai dengan menguningnya daun pada area inokulasi. Persentase keparahan penyakit terendah terjadi pada Xoo sebesar 4,12%, diikuti oleh B. oryzae sebesar 7,70%, dan P. oryzae sebesar 10,32%.
Berdasarkan hasil penelitian dapat disimpulkan bahwa, B. cereus terbukti dapat digunakan sebagai agen biokontrol untuk mengendalikan penyakit padi yang disebabkan oleh P. oryzae, B. oryzae dan Xoo. B. cereus juga mampu menghambat pertumbuhan ketiga patogen tersebut dengan persentase daya hambat di atas 50%. Selain itu, B. cereus juga mampu mengurangi keparahan penyakit hawar daun bakteri, serta memperpanjang masa inkubasi patogen, sehingga memberikan waktu tambahan bagi tanaman untuk bertahan dari serangan penyakit. Hal ini menunjukkan potensi besar B. cereus sebagai agen biokontrol dalam pengelolaan penyakit padi yang lebih ramah lingkungan dan berkelanjutan.

Rice (Oryza sativa L.) is a major food crop in Indonesia, but it is highly susceptible to attacks by plant pest organisms such as fungi and bacteria, which can significantly reduce production. Major rice diseases include blast disease caused by Pyricularia oryzae, brown leaf spot by Bipolaris oryzae and bacterial leaf blight (HDB) caused by Xanthomonas oryzae pv. oryzae (Xoo). The application of synthetic pesticides for disease control is a common practice, but has adverse effects on the environment. Therefore, more environmentally friendly control alternatives are needed, such as the use of endophytic bacteria, Bacillus cereus is reported to have potential as a plant pathogen biological control agent. This study aims to test the potential of B. cereus from rice plants in suppressing several rice plant pathogens through in vitro and in vivo experiments. This research was conducted in Plant Disease Laboratory and Gauze House, Faculty of Agriculture, Syiah Kuala University. This research consisted of 2 experimental stages, namely in vitro and in vivo. In the in vitro experiment, B. cereus antagonism test was conducted against the pathogens P. oryzae, B. oryzae and Xoo. This process involved the multiplication of B. cereus, P. oryzae, B. oryzae and Xoo cultures, followed by the antagonism test of B. cereus against the three pathogens. The parameter observed was the percentage inhibition of B. cereus against rice pathogens. In the in vivo experiment, rice resistance was induced using B. cereus, by immersing rice seeds and roots in a suspension of B. cereus suspension 109 cells/ml. Parameters observed included percentage of germinated seeds, incubation period and percentage of disease severity. Based on the results, the highest inhibition against P. oryzae, B. oryzae and Xoo was 79.16%, 68.21%, and 64.44%, respectively. Percentage of germinated seeds, seeds with soaking suspension of B. cereus suspension was superior at 89%. The longest incubation period for each pathogen was 12.33 days for P. oryzae, 12.16 days for B. oryzae, and 10.33 days for Xoo. Early symptoms in P. oryzae appeared oval-shaped necrosis and lighter in the middle, in B. oryzae it was characterized by the appearance of dark brown spots and in Xoo it was characterized by yellowing of leaves in the inoculation area. The lowest percentage of disease severity occurred in Xoo at 4.12%, followed by B. oryzae at 7.70%, and P. oryzae at 10.32%. Based on the results, it can be concluded that B. cereus can be used as a biocontrol agent to control rice diseases caused by P. oryzae, B. oryzae and Xoo. B. cereus was also able to inhibit the growth of the three pathogens with a percentage of inhibition above 50%. In addition, B. cereus was also able to reduce the severity of bacterial leaf blight, as well as extend the incubation period of the pathogen, thus providing additional time for plants to survive the disease attack. This shows the great potential of B. cereus as a biocontrol agent in rice disease management that is more environmentally friendly and sustainable.