Judul: Non-Pathogenic Phyllosphere Bacteria Producing Bioactive Compounds as Biological Control Agent of Xanthomonas oryzae pv. oryzae
Abstrak: Xanthomonas oryzae pv. oryzae (Xoo) merupakan penyebab penyakit Hawar Daun Bakteri (HDB) pada tanaman padi. Bakteri patogen ini menginfeksi tanaman melalui luka atau lubang alami pada daun. Kerusakan terberat terjadi ketika patogen menyerang tanaman rentan sehingga menimbulkan gejala kresek dan hawar daun yang menyebabkan kematian padi. Penggunaan pestisida dan bahan-bahan kimia berbahaya pada saat ini mulai ditinggalkan karena tidak ramah terhadap lingkungan. Perkembangan bioteknologi telah mendorong berkembangnya penelitian tentang penggunaan mikroorganisme sebagai agen biokontrol. Pemanfaatan bakteri filosfer padi sebagai agen biokontrol merupakan salah satu strategi alternatif untuk mengendalikan Xoo. Penelitian ini bertujuan untuk mencari potensi bakteri filosfer padi yang memiliki kemampuan antagonis terhadap Xoo dan bersifat non-patogenik terhadap tanaman, serta mempelajari kemampuan penghambatan isolat potensial tersebut terhadap bakteri Xoo, penyebab penyakit hawar daun bakteri pada tanaman padi, di rumah kaca., Xanthomonas oryzae pv. oryzae (Xoo) is a causative agent of bacterial leaf blight (BLB) disease in rice plant. These pathogenic bacteria infect the plants through wounds or natural openings on the leaves. The severest damage occurs when the pathogens invade susceptible plants which cause blight symptoms and affect to the death of the rice. The use of pesticides and chemicals that are harmful for environment are reduced nowadays. The development of biotechnology has pushed the research focus on the use of microorganisms as a bio-control agent. Utilization of rice phylosphere bacteria as bio-control agent is one alternative strategy for controlling Xoo. This study aimed to explore the potencies of phyllosphere bacteria as antagonistic agent to Xoo which non-pathogenic to plants, and study the inhibitory potencies of isolates to Xoo causing bacterial leaf blight in rice plants in greenhouse condition
Keyword: phyllosphere bacteria, bioactive compound, Xoo, biocontrol agent

Judul: Potensi Beberapa Bakteri Penghambat Pertumbuhan Xanthomonas oryzae pv. oryzae Penyebab Penyakit Hawar Daun Bakteri pada Tanaman Padi
Abstrak: Bacterial leaf blight (BLB) disease caused by plant pathogenic bacteria Xanthomonas oryzae pv. oryzae (Xoo) could lead to death of rice plants. Control of plant pathogenic bacteria can be performed using biological control agents. The aim of this research was to study the inhibitory ability of eight isolates of biocontrol bacteria against Xanthomonas oryzae pv. oryzae (Xoo) under greenhouse conditions. Isolates of biological agents used in the study were obtained from IPB Culture Collection (IPBCC), Department of Biology, IPB and microbial gene bank collection of Indonesian Center for Agriculture Biotechnology and Genetic Resources (BB Biogen), consisting of Pseudomonas aeruginosa C32a and C32b, P. fluorescens ATCC 13525 Pf , Serratia marcescens E31, Bacillus sp. I.5, B. cereus I.21 and II.14, and B. firmus E65 isolates. The methods used in the research i.e. hypersensitivity test, antagonistic test of biocontrol bacteria to Xoo, and in vivo application of biological agents in the greenhouse condition. Hypersensitivity test on tobacco plants using C32a and C32b inoculums showed characteristics of slightly leaf yellowing but did not cause necrosis. Injection using Xoo inoculum showed necrosis on tobacco leaves. Antagonist isolates i.e. C32a, C32b, Pf, I.21, and I.5 showed inhibitory activity against Xoo, whereas others isolates did not show inhibitory activity. In greenhouse experiments IR 64 rice plants were sprayed with biological control agents (107cfu/ml) at 7 days, 14 days, 28 days, and 42 days after planting. The results showed that C32a isolate could suppress better the lesion length of BLB than that of chemical control (copper sulphate). Growth measurement of rice plants were assessed on plant height, number of tillers, panicle number and grain weight. Rice plants spraying treatment with isolates E65, E31, C32a, C32b, I.21, Pf, and I.5 showed no difference with control of sterile distilled water. Spraying with each suspension isolate of I.21, E31, C32a, Pf, and C32b indicated no different in the panicle number, in addition rice production was higher in C32a, Pf, C32b, and I.21 treatments. Spraying with C32a isolates produced the highest grain production compared with that of other isolates.
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Judul: Closed Knight’s Tour pada Papan Catur Berbentuk Persegi Panjang dengan Ukuran Maksimal 8 × 8
Abstrak: Closed Knight’s Tour merupakan langkah kuda yang mengunjungi setiap kotak pada papan catur tepat satu kali dengan langkah kuda berawal dan berakhir pada kotak yang sama. Graf yang terbentuk dari closed knight’s tour dinotasikan sebagai graf G(m,n), dengan m adalah banyaknya baris dan n adalah banyaknya kolom. Graf tersebut memuat Hamiltonian cycle. Sebuah graf terhubung G adalah graf bipartite jika dan hanya jika graf tersebut tidak memiliki cycle dengan panjang ganjil. Papan catur yang memenuhi syarat cukup untuk memiliki closed knight’s tour adalah papan catur berukuran 5 × 6, 5 × 8, 6 × 6, 6 × 7, 6 × 8, 7 × 8, dan 8 × 8.
Keyword: bipartite, closed knight’s tour, hamiltonian cycle, knight’s tour, teori graf