Electronic Theses and Dissertation

Sclerotium rolfsii merupakan salah satu cendawan yang menjadi patogen utama penyebab penyakit busuk batang dan penyebarannya melibatkan tanah sebagai jalur penularan utama. Gejala awal ditandai dengan tanaman yang menguning dan layu, kemudian diikuti oleh munculnya akar tunggang yang lunak dan lembab. Dalam kasus infeksi yang parah, bisa mengakibatkan kematian seluruh tanaman. Umumnya, upaya pengendalian serangan cendawan S. rolfsii yaitu dengan penggunaan fungisida sintetik. Namun penggunaannya dapat memberikan dampak negatif seperti residu yang dapat mencemari lingkungan serta menimbulkan resistensi bagi organisme pengganggu tanaman (OPT). Oleh karena itu diperlukan alternatif pengendalian lain seperti penggunaan metabolit sekunder asal bakteri endofit B. thuringensis AK08 dan Arthrobacter sp. AM08. B. thuringensis AK08 dan Arthrobacter sp. AM08 dilaporkan dapat digunakan sebagai agens pengendali hayati dalam mengendalikan patogen penyebab penyakit pada tanaman, karena memiliki senyawa dan enzim yang bersifat antifungi. Penelitian ini dilakukan untuk mengetahui potensi metabolit sekunder asal bakteri endofit isolat lokal B. thuringiensis AK08 dan Arthrobacter sp. AM08 dalam menghambat pertumbuhan S. rolfsii secara in vitro.
Penelitian ini menggunakan Rancangan Acak Lengkap (RAL) non faktorial dengan empat perlakuan dan lima ulangan, setiap ulangan terdiri dari 2 unit sehingga diperoleh 40 unit percobaan. Potensi metabolit sekunder asal bakteri endofit isolat lokal B. thuringiensis AK08 dan Arthrobacter sp. AM08 diuji terhadap cendawan patogen S. rolfsii menggunakan metode difusi cakram. Cendawan S. rolfsii yang telah disuspensi sebelumnya dengan pengenceran 10-2 diambil sebanyak 1 ml kemudian dicampur dengan media PDA dan NA, dituangkan ke cawan petri yang sama lalu digoyangkan hingga homogen dan dibiarkan media mengeras. Kertas cakram direndam dalam ekstrak metabolit sekunder bakteri endofit hingga menyerap. Kertas cakram ditempatkan pada media agar yang mengandung suspensi S. rolfsii dan diinkubasi selama 7 hari. Peubah yang diamati meliputi waktu pertumbuhan koloni cendawan patogen S. rolfsii dan luas zona bening yang terbentuk.
Hasil penelitian menunjukkan bahwa waktu pertumbuhan koloni cendawan patogen S. rolfsii terlama ditunjukkan pada perlakuan metabolit sekunder Arthrobacter sp. AM08 yaitu pada 4,2 HSI, diikuti oleh perlakuan metabolit sekunder B. thuringiensis AK08 dan metabolit sekunder gabungan (B. thuringiensis AK08 ¬+ Arthrobacter sp. AM08) 3,5 HSI, serta perlakuan S. rolfsii (tanpa metabolit sekunder) 3,3 HSI. Selanjutnya, luas zona bening paling luas ditunjukkan pada perlakuan metabolit sekunder Arthrobacter sp. AM08 sebesar 17,60 mm. Diikuti oleh perlakuan metabolit sekunder gabungan (B. thuringiensis AK08 ¬+ Arthrobacter sp. AM08) sebesar 11,15 mm, perlakuan metabolit sekunder B. thuringiensis AK08 sebesar 3,60 mm, serta perlakuan S. rolfsii (tanpa metabolit sekunder) tidak membentuk zona bening sama sekali. Hasil penelitian ini dapat disimpulkan bahwa perlakuan metabolit sekunder asal bakteri endofit Arthrobacter sp. AM08 memiliki potensi yang mampu menghambat pertumbuhan S. rolfsii secara in vitro.

Sclerotium rolfsii is a fungus that is the main pathogen causing stem rot disease and its spread involves soil as the main transmission route. Initial symptoms are characterized by yellowing and wilting of the plant, followed by the appearance of a soft, moist taproot. In severe cases of infection, it can result in the death of the entire plant. Generally, efforts to control S. rolfsii fungus attack are through the use of synthetic fungicides. However, their use can have negative impacts such as residues that can pollute the environment and cause resistance to plant pest organisms (OPT). Therefore, other control alternatives are needed, such as the use of secondary metabolites from endophytic bacteria B. thuringensis AK08 and Arthrobacter sp. AM08. B. thuringensis AK08 and Arthrobacter sp. AM08 are reported to be used as biological control agents in controlling pathogens that cause disease in plants, because they have compounds and enzymes that are antifungal. This study was conducted to determine the potential of secondary metabolites from endophytic bacteria of local isolates B. thuringiensis AK08 and Arthrobacter sp. AM08 in inhibiting the growth of S. rolfsii in vitro. This study used a non-factorial Completely Randomized Design (CRD) with four treatments and five replicates, each replicate consisting of 2 units so that 40 experimental units were obtained. The potential of secondary metabolites from endophytic bacteria of local isolates B. thuringiensis AK08 and Arthrobacter sp. AM08 was tested against the pathogenic fungus S. rolfsii using the disc diffusion method. S. rolfsii fungus that had been previously suspended with a dilution of 10-2 was taken as much as 1 ml and then mixed with PDA and NA media, poured into the same Petri dish and then shaken until homogeneous and allowed the media to harden. Paper disks were soaked in the secondary metabolite extract of endophytic bacteria until it absorbed. The disc paper was placed on agar media containing S. rolfsii suspension and incubated for 7 days. The observed variables included the growth time of S. rolfsii pathogenic fungus colonies and the clear zone area formed. The results showed that the longest growth time of S. rolfsii pathogenic fungus colonies was shown in the Arthrobacter sp. AM08 secondary metabolite treatment at 4.2 HSI, followed by B. thuringiensis AK08 secondary metabolite treatment and combined secondary metabolite (B. thuringiensis AK08 ¬+ Arthrobacter sp. AM08) 3.5 HSI, and S. rolfsii treatment (without secondary metabolites) 3.3 HSI. Furthermore, the largest clear zone area was shown in the Arthrobacter sp. AM08 secondary metabolite treatment at 17.60 mm. Followed by the combined secondary metabolite treatment (B. thuringiensis AK08 ¬+ Arthrobacter sp. AM08) of 11.15 mm, secondary metabolite treatment of B. thuringiensis AK08 of 3.60 mm, and treatment of S. rolfsii (without secondary metabolites) did not form a clear zone at all. The results of this study can be concluded that the treatment of secondary metabolites from endophytic bacteria Arthrobacter sp. AM08 has the potential to inhibit the growth of S. rolfsii in vitro.