CHARACTERIZATION OF SOFT ROT BACTERIA OF SHALLOT IN JAVA

NOVITA PRAMAHSARI P., DR. TRI JOKO, SP., M.Sc; CHERIE GAMBLEY, PhD

2015 | Tesis | S2 Fitopatologi

Bawang merah merupakan tanaman hortikultura yang peting dan diroduksi di Indonesia dengan hasil produksi kurang lebih 9-11 ton.ha atau setengah dari produksi potensial yaitu 20 ton/ha. Penyakit tanaman merupakan salah satu kendala dari penurunan produksi bawang merah yang merusak hingga ditempat penyimpaan. Penelitian ini bertujuan untuk mengidentifiasi bacteri pathogen yang menyebakan penyakit busuk lunak pada bawang merah di lapangan maupun ditempat penyimpana. Isolasi bakteri penyebab busuk lunak diisolasi dengan medium nutrient agar, dan diperoleh 65 isolat bakteri yang dikumpulkan dari pusat penanaman bawang merah di Jawa. Bakteri penyebab busuk lunak di seleksi melalui pengujian reaksi gram hingga uji patogenisitas pada umbi bawang merah, bawang Bombay dan umbi kentang. Hasil seleksi tersebut menunjukan 25 isolat dapat menyebabkan busuk lunank pada umbi bawang merah, bawang Bombay dan kentang dan diseleksi dengan metode Rep-PCR menggunakan primer BOX-A1R dan ERIC menunjukan ada 10 grup isolate yang berbeda. Enam isolat diantaranya Xt, DKR, Str, CT, M4.3 dan M4.5 posistif pada pengujian hipersensitiv di daun tembakau dengan virtulensi tertinggi dalam menyebabkan busuk lunak pada umbi bawang merah, bawang Bombay dan kentang. Analisis filogenetik berdasarkan gen 16S-rDNA menunjukan isolat uji memiliki kedekatan dengan Pectobacterium carotovorum isolate Xt, Enterobacteria cloaceae isolat NGA2P, Klebsiella pneumonia isolat BW1.2, Providencia stuartii isolat PV2, Pseudomonas aeroginosa P.K1K, Serratia marcescens isolat TV1 and Stenotrophomonas maltophila isolat M10. Identifikasi bedasarkan gen gryB dan rpoD pada enam isolat terbaik juga menunjukan isolat tersebut merupakan Pectobacterium carotovorum subsp. carotovorum. Penelitian ini juga menunjukan adanya asosiasi antara E. cloaceae dan S. malthophila pada tanaman bawang merah Indonesia.

Shallot is very important spice vegetable and the production in Indonesia is only about 9-11 ton/ha or about a half of the potential production at about 20 ton/ha. The production constrains including plant diseases in the field or leading to destroy the product in the storage. This research is conducted to identify bacterial pathogens associated with soft rot disease of shallot in the field and in the storage. The medium of nutrient agar was used to isolate bacteria from the samples obtained from several shallot production centers in Java and 65 isolates were collected. The first soft rots bacterial selection was conducted for gram negative followed by inoculation on shallot bulb, onion bulb and potato tuber resulted on the number of 25 isolates were selected. Rep-PCR using BOX-A1R and ERIC primers were conducted resulted on 10 groups of isolates. Tobacco hypersensitivity tests was further conducted and only 1 rep-PCR cluster consisting 6 isolates were positive while the other 9 cluster isolates were negative. One isolate from the positive of tobacco hypersensitive reaction cluster resulted on the highest homology with Pectobacterium carotovorum based on the 16S-rDNA sequence from the gene bank. This P. carotovorum cluster consisting 6 isolates were further identified using genes of gyrB and rpoD resulted on the identical pattern closely related to P.c. subsp. carotovorum. The other 7 clusters of rep-PCR resulted on the identification of Enterobacteria cloaceae, Klebsiella pneumonia., Providencia stuartii., Pseudomonas aeroginosa, Serratia marcescens and Stenotrophomonas maltophila based on the sequence of the 16S-rDNA. This research is conducted further on the discovery of E. cloaceae and S. malthophila associated with shallot in Indonesia since those species are quite diverse as human pathogens, plant pathogens or biological control agents.

Kata Kunci : Shallot soft rot bacteria, Pectobacterium carotovorum subsp. carotovorum, Enterobacteria cloaceae, Stenothrophomonas maltophila