Judul: Eksplorasi Mikroba Rizosfer dan Hubungannya dengan Sifat Fisik & Kimia Tanah pada Tanaman Kelapa Sawit Terinfeksi Ganoderma boninense Pat.
Abstrak: Oil palm (Elaeis guineensis Jacq.) is one of the plantation crops which has a significance in contributing foreign exchange to the country from non-oil sector. One of the fence in development oil palm cultivation is the presence of stem rot disease caused by Ganoderma boninense. This research aims to explore the microbial rhizosphere surrounding to the oil palm plants, as well as its relationship to the condition of physical and chemical soil characteristics. The study was conducted by taking a surrounding soil of oil palm plantations as a sample and made its suspension. The suspension was made to serial dilutions to 10-8 dilution rate. In vitro antagonism test between antagonist candidate of actinomycetes to G. boninense conducted by using a dual culture methods. Observations were made by measuring the radial growth of pathogenic fungi and actinomycetes isolates were away from fingers pathogenic fungi actinomycetes isolates were approaching. The results of microbial isolation consist of 76.9% fungal isolates, 12.82% bacterial isolates, and 10.26% actinomycetes isolates. The content of chemical characteristics soil at the study was sited at pH 4.43 it is included in a slightly acid soil type and content of C/N ratio 8.78 is low. The results of in vitro experiments showed that isolate AK1 (actinomycetes 1), AK2 (actinomycetes 2), and AK3 (actinomycetes 3) have a significant effect on the growth of pathogenic G. boninense fungi on PDA at the fifth day.
Keyword: Ganoderma boninense, microbial rhizosphere, oil palm

Judul: Isolation, Identification, and Media Formulation of  Endophytic Bacteria to Limit Ganoderma Fungus Attacks on Oil Palm
Abstrak: Ganoderma boniense merupakan cendawan patogen yang menyebabkan penyakit busuk pangkal batang (BPB) pada tanaman kelapa sawit. Penelitian ini mengkaji suatu alternatif dalam mengendalikan G. boninense melalui pemanfaatan agens pengendali hayati (APH) yang lebih ramah lingkungan daripada penggunaan fungisida komersial. Seleksi bakteri endofit sebagai APH dilakukan melalui isolasi bakteri dari akar kelapa sawit, mengukur persen zona hambatan terhadap isolat G. boninense secara in vitro, dan uji hipersensitif pada tanaman tembakau. Isolat bakteri endofit terpilih A2 dan C5 memiliki daya hambat terhadap G. boninense berturut-turut sebesar 35% dan 47%. Kedua isolat tersebut teridentifikasi secara molekuler berturut-turut sebagai bakteri Lysinibacillus xylanilyticus (99,85%) dan bakteri Aeromonas hydrophila (99,64%). Bakteri endofit terpilih diformulasikan ke dalam formulasi kompos, tepung, dan cair. Ketiga jenis formula dapat mempertahankan viabilitas sel sampai dengan 106 cfu/ml serta lebih stabil dan adaptif pada formulasi cair dengan kepadatan berkisar (8,0–9,0)×106 cfu/ml pada akhir minggu pengamatan dibandingkan formulasi lainnya., Ganoderma boninense is a pathogenic fungus that causes basal stem rot (BSR) diseases in oil palm plantations. This research examined an alternative in controlling G. boninense through the use of biological control agents (BCAs) which was more environmentally friendly than the use of commercial fungicide. Endophytic bacteria as BCAs were selected by isolating bacteria from oil palm roots, measuring the percent zone of inhibition against G. boninense based on in vitro test, and presenting hypersensitivity test on tobacco plant. Selected endophytic bacterias namely A2 and C5 had inhibiton against G. boninense of 35% and 47%, respectively. Those isolates were identified molecularly as Lysinibacillus xylanilyticus (99,85%) and Aeromonas hydrophila (99,64%), respectively. The selected endophytic bacterias were formulated in compost, flour, and liquid formulation. Those three types of formula could maintain cell viability up to 106 cfu/ml and are more stable also adaptive in liquid formulation within a range of (8,0–9,0)×106 cfu/ml at the end of the observation compared to other formulations.
Keyword: basal stem rot (BSR), endophytic bacteria, Ganoderma boninense, media formulation, oil palm

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