Electronic Theses and Dissertation

Ringkasan fusarium sp. patogen tular tanah yang merupakan penyebab utama penyakit layu pada tanaman pala. patogen ini mampu menyerang tanaman dari fase benih hingga dewasa dan dapat bertahan lama di dalam tanah. salah satu teknik pengendalian yang sedang pesat perkembanganya saat ini adalah pemanfaatan mikroorganisme (bakteri saprofit nonpatogenik) yang dieksplorasi dari rizosfer tanaman (rhizobakteri). pendekatan pengendalian hayati melalui pemanfaatan bakteri saprofit dari rizosfer menjadi solusi potensial yang ramah lingkungan dan berkelanjutan. penelitian ini bertujuan untuk mengeksplorasi dan menguji kemampuan bakteri yang berasosiasi pada rizosfer tanaman pala sebagai agens antagonis terhadap fusarium sp. in vitro. penelitian dilakukan di laboratorium ilmu penyakit tumbuhan fakultas pertanian universitas syiah kuala. proses penelitian meliputi isolasi dan seleksi bakteri dari tanah rizosfer pala yang sehat, isolasi cendawan patogen dari tanaman pala sakit, serta uji patogenisitas, karakterisasi morfologi dan biokimia, serta uji antagonisme secara in vitro menggunakan metode dual culture. hasil penelitian, menunjukkan bahwa ditemukan sebanyak 33 isolat bakteri saprofit dari tanaman pala, 24 isolat memberikan hasil patogenesitas sedangkan 9 di antaranya yang bersifat non-patogenik (saprofit), berdasarkan uji patogenisitas pada tanaman tembakau. isolat-isolat saprofit ini kemudian dikarakterisasi, berdasarkan hasil karakterisasi morfologi secara makroskopis dan mikroskopis diduga beberapa isolat bakteri saprofit yang diperoleh dari rizosfer tanaman pala yang termasuk genus bacillus sp. (br1, br2, br14, br25, burkholdeia sp. (br6), flavobacterium sp. (br5 dan br23), acinobacter sp (br15), dan enterobacter sp. (br22) kemudian beberapa bakteri yang didapatkan dilanjutkan dengan uji daya hambat terhadap fusarium sp. hasil yang diperoleh burkholderia sp. flavobacterium sp1, dan bacillus sp3. memiliki efektivitas sangat tinggi dalam menghambat pertumbuhan cendawan patogen, dengan daya hambat yang tinggimpada hari2 awal. namun, efektivitas penghambatan cenderung menurun pada hari-hari berikutnya, yang diduga disebabkan oleh degradasi senyawa antagonistik. uji dual culture menunjukkan bahwa pada hari ke-7 setelah inokulasi (hsi) beberapa isolat, seperti bacillus sp1, bacillus sp2, flavobacterium sp1, acinetobacter sp, enterobacter sp., flavobacterium sp2, bacillus sp4 menghasilkan zona bening yang mengindikasikan adanya mekanisme antibiosis. isolat burkholderia memperlihatkan mekanisme overgrowth, sedangkan bacillus sp3 menunjukkan kompetisi ruang. namun pada hari ke-14 hsi, fusarium sp. mampu melakukan overgrowth terhadap hampir semua isolat bakteri, diduga karena menurunnya ketersediaan nutrisi dan aktivitas antibiosis bakteri. meskipun demikian, pengamatan mikroskopis memperlihatkan adanya kerusakan hifa fusarium seperti hifa melengkung, mengeriting, bercabang tidak beraturan, abnormal, dan septa memendek. kerusakan ini mengindikasikan aktivitas enzim hidrolitik (kitinase, β-1,3-glukanase) yang diproduksi oleh bakteri. secara keseluruhan, penelitian ini menyimpulkan bahwa bakteri saprofit asal tanaman pala tidak semuanya mampu berperan sebagai agens antagonis langsung, tetapi tetap memiliki peran penting dalam mendukung kesehatan tanaman. selain menekan patogen melalui antibiosis dan aktivitas enzimatik, bakteri saprofit berpotensi sebagai plant growth promoting rhizobacteria (pgpr) dan pemicu induced systemic resistance (isr) pada tanaman.

Fusarium sp. is a soil-borne pathogen that is the primary cause of wilt disease in nutmeg plants. This pathogen can attack plants from seedling stage to maturity and can survive for long periods in the soil. One control technique currently experiencing rapid development is the use of microorganisms (non-pathogenic saprophytic bacteria) extracted from the plant rhizosphere (rhizobacteria). A biological control approach utilizing saprophytic bacteria from the rhizosphere offers a potential, environmentally friendly and sustainable solution. This research aims to explore and test the ability of bacteria associated with the rhizosphere of nutmeg plants as antagonistic agents against Fusarium sp. in vitro. The research was conducted in the Plant Pathology Laboratory, Faculty of Agriculture, Syiah Kuala University. The research process included the isolation and selection of bacteria from healthy nutmeg rhizosphere soil, the isolation of pathogenic fungi from diseased nutmeg plants, and pathogenicity testing, morphological and biochemical characterization, and in vitro antagonism testing using the dual culture method. The results of the study showed that 33 isolates of saprophytic bacteria were found from nutmeg plants, 24 isolates gave pathogenicity results while 9 of them were non-pathogenic (saprophytic), based on pathogenicity tests on tobacco plants. These saprophytic isolates were then characterized, based on the results of macroscopic and microscopic morphological characterization, it was suspected that several isolates of saprophytic bacteria obtained from the rhizosphere of nutmeg plants belonged to the genus Bacillus sp. (BR1, BR2, BR14, BR25, Burkholdeia sp. (BR6), Flavobacterium sp. (BR5 and BR23), Acinobacter sp. (BR15), and Enterobacter sp. (BR22) Then several bacteria obtained were continued with an inhibitory test against Fusarium sp. The results obtained by Burkholderia sp. Flavobacterium sp1, and Bacillus sp3. had very high effectiveness in inhibiting the growth of pathogenic fungi, with high inhibitory power in the early days. However, the effectiveness of inhibition tended to decrease in the following days, which was thought to be caused by the degradation of antagonistic compounds. Dual culture tests showed that on the 7th day after inoculation (DAI), several isolates, such as Bacillus sp1, Bacillus sp2, Flavobacterium sp1, Acinetobacter sp, Enterobacter sp., Flavobacterium sp2, and Bacillus sp4, produced clear zones, indicating the presence of an antibiosis mechanism. The Burkholderia isolate exhibited overgrowth, while Bacillus sp3 exhibited competition for space. However, on the 14th day after inoculation (DAI), Fusarium sp. overgrew almost all bacterial isolates, likely due to decreased nutrient availability and bacterial antibiosis activity. However, microscopic observations revealed damage to Fusarium hyphae, including curved, curled, irregularly branched, and abnormal hyphae, with shortened septa. This damage indicates the activity of hydrolytic enzymes (chitinase, β-1,3-glucanase) produced by the bacteria. Overall, this study concludes that not all saprophytic bacteria native to nutmeg plants are capable of acting as direct antagonists, but they still play an important role in supporting plant health. In addition to suppressing pathogens through antibiosis and enzymatic activity, saprophytic bacteria have the potential to act as plant growth promoting rhizobacteria (PGPR) and trigger induced systemic resistance (ISR) in plants.