Pengendalian Penyakit Busuk Bulir Bakteri (Burkholderia glumae) pada Tanaman Padi menggunakan Teknik Biopriming dengan Bakteri Endofit

Abstract

Penyakit busuk bulir bakteri yang disebabkan oleh Burkholderia glumae merupakan penyakit penting karena dapat menurunkan hasil panen padi. Bakteri ini tergolong penyakit tular benih yang mampu menyebabkan kerugian hingga 75%. Pengendalian biologi dengan menggunakan bakteri endofit merupakan salah satu alternatif pengendalian penyakit ini. Biopriming merupakan teknik yang menginokulasikan benih dengan mikroba bermanfaat untuk menjaga benih dari cekaman biotik dan abiotik. Penelitian ini bertujuan untuk mengevaluasi dan menyeleksi potensi bakteri endofit asal tanaman padi sebagai agens biopriming untuk mengendalikan penyakit busuk bulir. Tahapan penelitian dilakukan dalam enam tahap, yaitu: 1) isolasi bakteri endofit, 2) penapisan isolat bakteri endofit berdasarkan uji keamanan hayati yang meliputi uji reaksi hipersensitivitas dan uji kemampuan menghidrolisis darah, 3) uji antagonisme secara in vitro, 4) uji pertumbuhan dan perkecambahan benih padi, 5) pengendalian penyakit melalui aplikasi sebagai agen biopriming, 6) karakterisasi bakteri endofit mencakup pengujian sifat Gram, uji aktivitas senyawa organik volatil, uji produksi Indole-3-Acetic-Acid, dan identifikasi secara molekuler dengan sekuensing gen 16S rRNA terhadap isolat bakteri endofit yang paling potensial. Hasil penelitian diperoleh sebanyak 133 bakteri endofit berhasil diisolasi dari tiga jenis tanaman padi yaitu padi putih (varietas Ciherang dan Inpari IR Nutri Zinc), padi merah (varietas Inpari 24 dan Inpari Arumba), dan padi ketan (varietas Paketih dan Setail). Sebanyak 27 isolat berhasil lolos dari seleksi keamanan hayati (uji hemolisis dan uji reaksi hipersensitivitas). Delapan isolat bakteri endofit yang didapatkan menunjukkan antagonisme terhadap B. glumae secara in vitro. Berdasarkan metode analytical hierarchy process (AHP), terpilih 3 isolat paling potensial sebagai agens biopriming terhadap B. glumae, yaitu BBZN3, BBAR4 dan AKPAT4. Ketiga isolat endofit BBZN3, BBAR4, dan AKPAT4 mampu menurunkan populasi B glumae dalam benih, menurunkan insidensi dan keparahan penyakit, dan meningkatkan pertumbuhan tanaman padi varietas Ciherang. Hasil karakterisasi ketiga isolat tersebut tergolong dalam bakteri gram positif, mampu memproduksi IAA kecuali isolat BBAR4, dan dapat memproduksi senyawa volatil yang dapat menghambat perkembangan B. glumae. Diantara ketiga isolat bakteri endofit tersebut, AKPAT4 merupakan isolat bakteri yang menunjukkan kemampuan terbaik sebagai agens biokontrol terhadap B. glumae. Berdasarkan sekuens 16S rRNA, isolat AKPAT4 diidentifikasi sebagai Bacillus cereus. Hasil penelitian ini mengindikasikan bahwa bakteri endofit tanaman padi putih, padi merah, dan padi ketan berpotensi dalam mengendalikan B. glumae melalui teknik biopriming.

Bacterial grain rot caused by Burkholderia glumae is an important disease of rice, which caused reduction of rice yields. This bacteria is classified as a seed-borne pathogen which caused losses up to 75%. Biological control using endophytic bacteria is one of the alternatives to control this disease. Biopriming is a technique that inoculates seeds with beneficial microbes to protect seeds from biotic and abiotic stress.This study aims to evaluate and select the potential of endophytic bacteria from rice plants as biopriming agents to control grain rot disease. The research was conducted in six stages, i.e: 1) isolation of endophytic bacteria, 2) screening the endophytic isolates based on biosafety test through hypersensitive reaction and hemolysis reaction, 3) in vitro antagonism test, 4) growth and germination tests rice seeds, 5) disease control by application as biopriming agents, 6)characterization of endophytic bacteria include testing Gram, volatile organic compound activity, Indole-3-Acetic-Acid production, and molecular identification by 16S rRNA gene sequencing of the prospective isolates of endophytic bacteria. The result of the study showed that 133 endophytic bacteria were successfully isolated from three types of rice plants, namely white rice (Ciherang and Inpari IR Nutri Zinc varieties), red rice (Inpari 24 and Inpari Arumba varieties), and glutinous rice (Paketih and Setail varieties). A total of 27 isolates successfully passed the biosafety selection (hemolysis test and hypersensitivity reaction test). Eight endophytic bacterial isolates obtained showed antagonism to B. glumae in vitro. Based on the analytical hierarchy proccess (AHP) turned out that two endophytic isolates (isolate AKSET6 and isolate BBSET1) had toxic effects that inhibited seed germination. Based on the analytical hierarchy process (AHP) method, the 3 most potential isolates were selected as biopriming agents against B.glumae, namely BBZN3, BBAR4, and AKPAT4. The three potential endophytic isolates BBZN3, BBAR4, and AKPAT4 were able to reduce the population of B. glumae in seeds, reduce the incidence and severity of the disease, and increase the growth of Ciherang rice plants. The characterization results of the three isolates were classified as gram-positive bacteria, could produce IAA except isolate BBAR4, and could produce volatile compounds that could inhibit the development of B. glumae. Among the three endophytic bacterial isolates, AKPAT4 is the bacterial isolate that shows the best ability as a biocontrol agents against B. glumae. Based on the 16S rRNA sequence, the AKPAT4 isolate was identified as Bacillus cereus. The results of this study indicate that endophytic bacteria of white rice, red rice, and glutinous rice plants have the potential to control B. glumae through biopriming techniques.