Studi pengendalian hayati penyakit layu bakteri (Ralstonia Solanacearum) Nilam dengan Pseudomonad Fluoresen

NASRUN, Promotor Prof.Dr.Ir. Christanti, S.SU

2005 | Disertasi | S3 Ilmu Pertanian (Fitopatologi)

Tujuan penelitian ini adalah untuk mendapatkan pseudomonad fluoresen yang efektif untuk mengendalikan penyakit layu bakteri nilam, dan mengevaluasi pengaruhnya terhadap pertumbuhan dan produksi minyak nilam. Di samping itu juga untuk mengkarakterisasi patogen (Ralstonia solanacearum). Penelitian ini meliputi beberapa percobaan yaitu : karakterisasi bakteri patogen dan seleksi pseudomonad fluoresen (dilakukan di laboratorium Bakteriologi Tumbuhan dan rumah kaca Fakultas Pertanian Universitas Gadjah Mada, Yogyakarta). Deteksi mekanisme kompetisi ruang dan nutrisi (dilakukan di laboratorium dan rumah kaca Kebun Percobaan Laing Balai Penelitian Tanaman Rempah dan Obat (Balittro) Solok, Sumatera Barat). Percobaan pengendalian penyakit layu bakteri nilam di lapangan (dilakukan di kebun petani nilam di Pasaman Barat, Sumatera Barat). Analisis patchouli alkohol (dilakukan di laboratorium Balittro Bogor). Hasil penelitian menunjukkan bahwa penyakit layu bakteri nilam disebabkan oleh Ralstonia solanacearum ras 1 biovar III. Dari rizosfer nilam didapatkan 200 isolat pseudomonad fluoresen, dan 143 dari isolat-isolat tersebut menghambat pertumbuhan R. solanacearum secara in vitro dengan zona penghambatan 1- 40 mm dan mempunyai aktivitas bakteriostatik dan bakterisidal. Dua puluh lima isolat pseudomonad fluoresen yang mempunyai zona penghambatan di atas 20 mm, diseleksi untuk pengujian antagonistik di rumah kaca. Hasilnya menunjukkan bahwa sebagian besar isolat tersebut dapat menekan intensitas penyakit antara 3,33-68,33% dengan masa inkubasi 22-45 hari. Lima isolat pseudomonad fluoresen (Pf 63, Pf 90, Pf 91, Pf 147, dan Pf 180) yang menunjukkan daya antagonistik tinggi atau intensitas penyakit rendah, yaitu antara 3,33 – 13,33%, diuji lanjut di lapangan. Hasil percobaan lapangan menunjukkan bahwa pada nilam yang diperlakukan dengan pseudomonad fluoresen terjadi penekanan intensitas penyakit secara nyata yaitu dari 82,78% menjadi 32,22 – 51,67%, dan memperpanjang masa inkubasi dari 22 menjadi 32 – 78 hari. Pengamatan pertumbuhan tanaman menunjukkan bahwa tanaman yang diperlakukan dengan pseudomonad fluoresen menghasilkan pertumbuhan lebih baik yaitu : tinggi tanaman (39,7-59,3 cm) dan jumlah daun lebih banyak (27,8-53,3 daun/tanaman) dibandingkan dengan tanaman yang tidak diperlakukan. Begitu pula dengan produksi daun kering dan minyak nilam dari tanaman yang diperlakukan dengan pseudomonad fluoresen lebih tinggi yaitu daun kering 435–1.733 g/petak ; jumlah minyak 8,33–25,8 ml/petak; rendemen minyak 1,91-2,30%, dan kandungan patchouli alkohol 33,38– 42,2% dibandingan dengan tanaman yang tidak diperlakukan. Isolat Pf 91 mempunyai pengaruh antagonistik lebih tinggi dari pada isolat lainnya. Penelitian dinamika populasi menunjukkan bahwa isolat pseudomonad fluoresen Pf 91 induk dan Pf 91rif/nal mempunyai daya tumbuh dan antagonistik yang sama secara in vitro. Percobaan rumah kaca menunjukkan kedua isolat tersebut mempunyai daya penekanan perkembangan penyakit yang sama. Populasi patogen (isolat Ns31) menurun secara nyata lebih besar dari populasi Pf 91 rif/nal. Penekanan populasi patogen diduga disebabkan oleh kompetisi ruang dan nutrisi dengan antagonis Pf 91 rif/nal.

The objectives of this study were to find out effective fluorescent pseudomonads for controlling bacterial wilt disease of patchouli plant, as well as to evaluate its effect on the plant growth and the production of patchouli oil. It also aimed to characterize the pathogen (Ralstonia solanacearum). The study involved several trials i.e. characterisation of bacterial pathogen and selection of fluorescent pseudomonads which were carried out in the laboratory of Plant Bacteriology and in screen house of Faculty of Agriculture, Gadjah Mada University, Yogyakarta. The detection of competitive mechanism on space and nutrient was carried out in the laboratory of Experimental Field Laing of the Indonesian Spice and Medicinal Crops Research Institute (ISMECRI) Solok, West Sumatra. The experiment of bacterial wilt disease control on patchouli plant was carried out in a farmer’s field in Pasaman, West Sumatra. Analysis of patchouli alcohol in patchouli oil was carried out in laboratory of the ISMECRI Bogor. Results of the study showed that the bacterial wilt disease was caused by Ralstonia solanacearum Race 1 biovar III. From the rhizosphere of patchouli plant, 200 fluoresecent pseudomonads isolates were collected and 143 isolates inhibited the growth of R. solanacearum in vitro with the inhibition zone of 1 – 40 mm. They have bacteriostatic and bactericidal activities. Twenty five isolates of fluorescent pseudomonads which showed inhibition zone more than 20 mm were selected for antagonistic test in screen house. The result showed that most of the fluorescent pseudomonads isolates were able to suppress development of bacterial wilt disease with the incubation period of 22-45 days, and disease intensity 3.33-68.33%. Five isolates of fluorescent pseudomonads ( Pf 63, Pf 90, Pf 91, Pf 147 and Pf 180) which showed high antagonistic activity or low disease intensity between 3.33-13.33% were tested further in the field. The result of field experiment showed that disease intensity of the plants treated with fluorescent pseudomonads significantly decreased from 82.78 % to 32.22 – 51.67%, and delayed incubation period from 26 to 32-78 days. Plant growth assessment showed that plants treated with the fluorescent pseudomonads stimulated higher plant growth i.e. plant height (39.7-59.3 cm), leaf numbers (27.8-53.3 leave/plant) than the untreated. In addition, production of dry leave and patchouli oil from the plants treated with fluorescent pseudomonads were higher i.e. 435-1.733 g/ plot in dry weight leave; 8.33 – 25.8 ml/plot in oil content; 1.91-2.30% in oil content, and 33.38-42.2% in patchouli alcohol content compared to the untreated. Pf 91 isolate has the highest antagonistic effect than the other isolates. Study on the population dynamic of fluorescent pseudomonads Pf 91wild type and Pf 91 Rif/nal showed that they have the same growth rate and antagonistic activity in vitro. They also have the same activity to suppress development of disease symptoms in screen house experiment. Population of the pathogen (Ns31 isolate) decreased more significantly than that of Pf 91Rif/nal. Reduction in the pathogen population is suspected due to competition of space and nutrient with the antagonist Pf 91Rif/nal.

Kata Kunci : Penyakit Layu Bakteri, Nilam, Pseudomonad Fluoresen