Electronic Theses and Dissertation

Tanaman nilam (Pogostemon cablin Benth.) merupakan salah satu komoditas perkebunan penting yang menghasilkan minyak atsiri bernilai tinggi ekonomi tinggi. Namun, produktivitas tanaman nilam kerap mengalami penurunan akibat serangan penyakit, salah satunya adalah penyakit layu bakteri yang disebabkan oleh Ralstonia solanacearum. Penyakit ini sangat merusak dan sulit dikendalikan karena kemampuan patogen bertahan lama di tanah. Pengendalian penyakit layu bakteri masih mengandalkan penggunaan pestisida kimia. Pemanfaatan bakteri endofit sebagai agensia hayati, dilaporkan memiliki potensi untuk menekan pertumbuhan patogen. Penelitian ini bertujuan untuk menguji potensi metabolit sekunder bakteri endofit asal tanaman nilam dalam menghambat pertumbuhan Ralstonia solanacearum.
Metode penelitian yang dilakukan untuk uji laboratorium adalah karakterisasi makroskopis dan mikroskopis, karakteristik biokimia dari isolat bakteri endofit, serta uji metabolit sekunder bakteri endofit isolat Bacillus sp1, klebsiella dan Bacillus sp2 terhadap Ralstonia solanacearum menggunakan metode difusi kertas cakram, sedangkan uji efektivitas dari isolat bakteri endofit dilapangan menggunakan metode observasi dilakukan dengan cara penyemprotan daun tanaman nilam (foliar spray), menggunakan tudor sprayer sampai permukaan daun basah, selanjutnya dilakukan penyiraman akar (soil drench), sebanyak 10 ml dengan konsentrasi ±10⁸ CFU/ml. Tujuh hari kemudian dilanjutkan dengan aplikasi bakteri patogen Ralstonia solanacearum dengan cara penyuntikan pada pangkal batang tanaman nilam.
Hasil penelitian dilaboratorium menunjukkan berdasarkan karakteristik makroskopis dan mikroskopis serta karakteristik biokimia dari tiga isolat bakteri endofit menunjukkan bahwa isolat bakteri endofit Bacillus sp1 dan Bacillus sp2 mempunyai kesamaan karakteristik dengan bakteri genus Bacillus, sedangkan isolat bakteri Klebsiella memiliki karakteristik yang sama dengan bakteri genus klebsiella. Daya hambat metabolit sekunder dari isolat bakteri endofit terhadap R. solanacearum melalui uji zona bening menunjukkan bahwa ketiga isolat bakteri endofit tersebut memiliki daya hambat yang lemah. Hasil uji lapangan suspensi bakteri endofit terhadap R. solanacearum menunjukkan bahwa efektifitas isolat bakteri endofit yang tertinggi adalah isolat Bacillus sp1 (tanpa adanya gejala), diikuti isolat Klebsiella dengan presentase serangan 54,09%, sedangkan isolat Bacillus sp2 tidak efektif.

Patchouli (Pogostemon cablin Benth.) is an important plantation commodity that produces essential oils with high economic value. However, patchouli productivity often declines due to disease attacks, one of which is bacterial wilt caused by Ralstonia solanacearum. This disease is highly destructive and difficult to control due to the pathogen's ability to persist in the soil. Bacterial wilt control still relies on the use of chemical pesticides. The use of endophytic bacteria as biological agents has been reported to have the potential to suppress pathogen growth. This study aims to test the potential of secondary metabolites from endophytic bacteria from patchouli plants to inhibit the growth of Ralstonia solanacearum. The research methods used for laboratory testing included macroscopic and microscopic characterization, biochemical characteristics of endophytic bacterial isolates, and secondary metabolite testing of Bacillus sp1, Klebsiella, and Bacillus sp2 isolates against Ralstonia solanacearum using the paper disc diffusion method. The effectiveness of the endophytic bacterial isolates in the field was tested using an observational method. Foliar spraying of patchouli leaves was performed using a Tudor sprayer until the leaf surface was wet. Subsequently, 10 ml of soil drench was applied to the roots at a concentration of approximately 10⁸ CFU/ml. Seven days later, the pathogenic bacteria Ralstonia solanacearum was applied by injection into the base of the patchouli plant stem. The results of the laboratory study showed that, based on the macroscopic and microscopic characteristics, as well as the biochemical characteristics of the three endophytic bacterial isolates, Bacillus sp1 and Bacillus sp2 isolates shared characteristics with bacteria of the genus Bacillus, while the Klebsiella isolates shared characteristics with bacteria of the genus Klebsiella. The inhibitory power of secondary metabolites from endophytic bacterial isolates against R. solanacearum through the clear zone test showed that the three endophytic bacterial isolates had weak inhibitory power. The results of the field test of endophytic bacterial suspensions against R. solanacearum showed that the highest effectiveness of endophytic bacterial isolates was Bacillus sp1 isolate (without symptoms), followed by Klebsiella isolates with an attack percentage of 54.09%, while Bacillus sp2 isolates were ineffective.