PENGARUH PUPUK HAYATI TERHADAP KOMUNITAS RIZOBAKTERI DAN PERKEMBANGAN LAYU FUSARIUM PADA TANAMAN PISANG

SUDARMONO, Prof. Dr. Ir. Siti Subandiyah, M.Agr.Sc

2014 | Tesis | S2 Bioteknologi

Layu fusarium merupakan penyakit paling mematikan bagi tanaman pisang dan disebabkan oleh jamur Fusarium oxsporum f.sp cubense (Foc). Berbagai macam cara telah dilakukan untuk mengatasi keganasan penyakit ini, salah satunya adalah penggunaan pupuk hayati. Penelitian ini bertujuan untuk melihat pengaruh pupuk hayati terhadap perkembangan penyakit layu fusarium serta terhadap komunitas rizobakteri di rizosfer tanaman pisang yang diperlakukan dengan pupuk hayati serta mengetahui bakteri apa saja yang berasal dari pupuk hayati dan rizosfer tanaman yang dapat menghambat pertumbuhan Foc secara invitro. Pada eksperimen lapangan, digunakan 4 perlakuan yaitu penggunaan pupuk M, pupuk O, pupuk sintetik, ditambah kontrol. Pengamantan kelayuan dilakukan setiap bulan. Analisis komunitas dilakukan dengan teknik PCR-RISA (Polymerase Chain Reaction-Ribosomal Intergenic Spacer Analysis) secara dependen kultur setiap 3 bulan. Bakteri rizosfer dan pupuk hayati diuji penghambatannya terhadap Foc secara in vitro dengan metode oposisi langsung. Bakteri yang menunjukkan daya hambat yang besar kemudian diseleksi dengan menggunakan teknik rep- PCR. Selanjutnya dilakukan identifikasi bakteri antagonis dari tanah dan pupuk hayati dengan menggunakan sekuen gen 16S rRNA dan gyrB. Hasil penelitian menunjukkan bahwa aplikasi pupuk O dapat menurunkan kelayuan sebesar 31,57%. Sementara kelayuan tanaman yang diperlakukan dengan pupuk M hanya 5,74% lebih rendah dibandingkan kontrol. Sesuai dengan perhitungan kerapatan secara mikrobiologi dan analisis komunitas dengan menggunakan teknik PCR-RISA, aplikasi pupuk hayati ditunjukkan dapat meningkatkan densitas dan diversitas bakteri di daerah rizosfer tanaman. Berdasarkan sekuen 16S rRNA, pada pupuk M dan O diperoleh isolat yang berkertabat dekat dengan kelompok Bacillus subtilis dan kelompok Bacillus cereus. Berdasarkan sekeun gen gyrB, isolat yang berasal dari pupuk hayati adalah Bacillus subtilis dan kelompok Bacillus cereus. Sementara isolat yang berasal dari tanah teridentifikasi sebagai Bacillus subtilis, Bacillus amyloliquefaciens dan kelompok Bacillus cereus.

Fusarium wilt is the most destructive disease of banana and caused by Fusarium oxsporum f.sp cubense (Foc). Various ways have been done against this disease. One is application of biological fertilizer containing biocontrol agent which is able to decrease the growth and infection of Foc pathogen to banana. In this study we evaluated the effect of biological fertilizer to fusarium wilt development and to the rhizobacterial community structure of rhizosphere of banana crop applied by biological fertilizer and to know what bacteria isolated from biological fertilizer and banana rhizosphere could inhibit the Foc growth invitro. In the field experiment, it was used random complete block desaign with 4 treatments, namely applied by biofertilizer M, biofertilizer O, synthetic fertilizer, and control. Application of the fertilizer was conducted before and every three months after plantation. Analysis of community was done by culturing bacteria isolated from rhizospheric soil which taken before, three month, and six month after plantation, then analyzed by dependent culture of PCR-RISA (Polymerase Chain Reaction-Ribosomal Intergenic Spacer Analysis). Bacteria isolated from both biological fertilizer and banana rhizosphere were tested to evaluate their invitro inhibitory activity to Foc by dual-culture method. Bacterial isolates showing large inhibition was selected by using rep-PCR technique to select the different strain for farther analysis. Finally, they are identified using 16S rRNA and gyrB gene sequences. This study show that application of Biofertilizer O could decreased the wilt to 31,57%. While the wilt of crop applied by biofertilizer M was 5,74% under the control only. The measurement of microbiologically density and analysis of bacterial community using PCR-RISA show that application of the biofertilizer could increase the diversity and density of the bacteria lived in plant rhizosphere. Based on 16S rRNA sequences, the 5 antagonistic biofertilizer bacteria are closely related to the group of Bacillus subtilis and group of Bacillus cereus. Based on gene gyrB sequence, bacterial isolate of the biofertilizer are include in Bacillus subtilis and group of Bacillus cereus. Whilst bacteria isolated from plant rhizosphere are identified as Bacillus subtilis, Bacillus amyloliquefaciens and group of Bacillus cereus.

Kata Kunci : Pupuk hayati, layu fusarium, Fusarium oxysporum pv. cubense, teknik PCR-RISA, teknik rep-PCR, gen 16S rRNA, gen gyrB.