Penapisan Rizobakteri asal Rizosfer Tanaman Lada Penghasil Senyawa Bioaktif Antifungi Fitopatogen

Abstract

Rizobakteri merupakan bakteri yang hidup di sekitar perakaran tanaman (rizosfer) dan dikenal sebagai Plant Growth Promoting Rhizobacteria karena kemampuannya dalam mendukung pertumbuhan tanaman. Rizobakteri menghasilkan metabolit sekunder seperti senyawa bioaktif antifungi untuk menghambat pertumbuhan fungi fitopatogen. Penelitian ini bertujuan menapis rizobakteri asal rizosfer tanaman lada yang memiliki aktivitas antifungi terhadap Fusarium oxysporum dan Rhizoctonia solani, mengetahui senyawa bioaktif dalam ekstrak rizobakteri, serta identifikasi gen 16S rRNA isolat terpilih. Uji aktivitas antifungi secara in vitro melalui metode dual culture dilakukan terhadap 19 isolat rizobakteri asal tanaman lada. Sebanyak dua isolat rizobakteri yang mempunyai aktivitas antifungi tertinggi dipilih untuk diekstraksi metabolit sekundernya dan dianalisis senyawa bioaktifnya menggunakan instrumen Gas Chromatography-Mass Spectrometry (GC-MS). Hasil uji aktivitas antagonistik menunjukkan, dari 19 isolat yang diuji, 6 isolat memiliki aktivitas antifungi terhadap F. oxysporum, dan 8 isolat mempunyai aktivitas antifungi terhadap R. solani. Aktivitas tertinggi terhadap F. oxysporum ditunjukkan oleh isolat BM3A5 (14,7%), sedangkan terhadap R. solani ditunjukkan oleh isolat TR212 (39%). Ekstrak kasar kedua isolat terpilih (BM3A5 dan TR212) menunjukkan bahwa keduanya memiliki senyawa bioaktif antifungi. Kelimpahan senyawa bioaktif tertinggi berdasarkan analisis GC-MS pada ekstrak kasar BM3A5 dan TR212 masing-masing adalah Benzeneacetic acid dan n-Hexadecanoic acid. Melalui analisis gen 16S rRNA menunjukkan isolat BM3A5 memiliki kemiripan dengan Enterobacter hormaechei ATCC 49162 dan TR212 dengan Bacillus cereus ATCC 14579.

Rhizobacteria are bacteria that live in the area around plant roots (rhizosphere) and are known as Plant Growth Promoting Rhizobacteria due to their ability to support plant growth. Rhizobacteria produce secondary metabolites such as antifungal bioactive compounds to inhibit the growth of phytopathogenic fungi. This study aimed to screen rhizobacteria isolated from the rhizosphere of pepper plants for their antifungal activity against Fusarium oxysporum and Rhizoctonia solani, identify bioactive compounds in the bacteria extracts, and determine the 16S rRNA gene sequence of selected isolates. Antifungal activity was conducted in vitro using dual culture method. A total 19 rhizobacteria isolates from pepper plants tested. Two rhizobacteria isolates with the highest antifungal activity were selected for secondary metabolites extraction and bioactive compounds analysis using Gas Chromatography-Mass Spectrometry (GC-MS). The antagonistic activity results showed that 6 out 19 isolates exhibited antifungal activity against F. oxysporum, and 8 isolates against R. solani. The activity against F. oxysporum was performed by isolate BM3A5 (14,7%), whereas against R. solani, it was performed by isolate TR212 (39%). Crude extracts of both isolates (BM3A5 and TR212) contained antifungal bioactive compounds. GC-MS analysis revealed that the most abundant bioactive compounds in the crude extracts from BM3A5 and TR212 were Benzeneacetic acid and n-Hexadecanoic acid, respectively. The 16S rRNA gene analysis showed that BM3A5 had the closest similarity with Enterobacter hormaechei ATCC 49162 and TR212 with Bacillus cereus ATCC 14579.