ISOLASI DAN KARAKTERISASI BAKTERI INDIGENOUS (Bacillus Cereus FRANK.) SEBAGAI AGENSIA PENGENDALI HAYATI HAMA KUBIS

Abstract

B. cereus strains were isolated from three district of North Sulawesi. The B. cereus strains are potentialindigenous bacteria for biological control agent against P. xylostella. The B. cereus strains were isolatedusing Ohba and Aizawa methods. Two hundred and two isolates putatively were isolated and identifiedas member of species B. cereus. Subseguently, representing isolates were selected to be screened forthe ability to kill P. xylostella. The screening test was conducted by using leaf depped methods with theconcentration of 1,22x108 spore/ml. The potential to kill test insect was assessed by mortality value. Theresult indicated that 10 isolates out of 15 of could produce mortality of insect from 50 to 100% afterexposure of 96 hours. It was confirmed that based on symptoms produced as well as bacterialcharacteristics reisolated from cadaver of test insect, the death of the test insects was certainly causedby application of bacterial isolates. It could be concluded that indigenous bacterial isolates identified tobe member of B. cereusare potential for biological control agent against P. xylostella. ABSTRAKUntuk memperoleh bakteri yang berpotensi sebagai agensia pengendali hayati hama Plutela.xylostelladilakukan isolasi dan karakterisasi bakteri indigenous. (Bacillus cereus) yang diperoleh dari sampeltanah yang berasal dari tiga kabupaten di Sulawesi utara. Bakteri diisolasi dengan metode Ohba danaizawa. Dari 103 sampel tanah yang digunakan dapat diperoleh 202 isolat yang diidentifikasi sebagaianggota spesies B.cereus. Sebanyak 15 isolat dipilih untuk mewakili seluruh isolat dalam sereening ujikemampuan membunuh P.xylostella. Pengujian dilakukan dengan metode pencelupan daun (leafdipped method) pada konsentrasi 1,22x108 spora/ml. Kemampuan membunuh serangga uji dinyatakandengan nilai mortalitas setelah pendedahan selama 96 jam. Ternyata hanya 10 isolat yang dapatmenimbulkan mortalitas serangga uji dengan kisaran 50%-100%. Berdasarkan gejala penyakit yangmuncul, karakteristik bakteri hasil reisolasi dari cadaver serangga mati menunjukkan bahwa kematianserangga uji dipastikan disebabkan oleh isolat bakteri yang diberikan. Disimpulkan, bahwa isolat bakteriindigenous anggota spesies B.cereus yang diperoleh berpotensi untuk dikembangkan menjadi kandidatagensia pengendali hayati bagi serangga hama kubis P.xylostella.