Judul: Aplikasi Kompos yang diperkaya Asam Humat dan Bakteri Endofit untuk Pengendalian Penyakit Blas pada Tanaman Padi
Abstrak: Blast disease caused by Pyricularia oryzae Cavara is an important disease of rice in Indonesia. This study aimed to examine the effect of humic acid on the growth of nonpathogenic endophytic bacteria in vitro and examine the effect of humic acid enriched compost and endophytic bacteria in vivo to control rice blast disease in plants caused by P. oryzae. The research methods consisted of isolation of endophytic bacteria stems and leaves of rice; tests in vitro by growing non- pathogenic endophytic bacteria on growing media with humic acid concentration level 0.1%, 0.2%, and 0.5%; characterization of selected bacteria; and in vivo testing applying compost enriched with endophytic bacteria i.e. bacteria I and humic acid with a concentration of 0.2%. The treatments were tested, namely a positive control, negative control, humic acid, bacteria I, humic acid + bacteria I. In vitro tests showed that bacteria I could grow well at a concentration of 0.2%. Then, the in vivo test application of humic acid could reduce the disease severity of 7.52%.
Keyword: the rice plant, P. oryzae, compost, blast, endophytic bacteria, humic acid

Judul: Potensi aktinomiset endofit dalam mengendalikan penyakit hawar daun bakteri pada tanaman padi (Oryza sativa)
Abstrak: Bacterial Leaf Blight (BLB) caused by Xanthomonas oryzae pv. oryzae (Xoo) is the most damaging disease in lowland rice growing areas in Indonesia. Endophytic actinomycetes provide advantages to the host plant through enhancement of plant physiological activity or through other modes of action and serve as source of agroactive compounds which can be used as biocontrol agent. The objectives of this experiments were to examine the potency of endophytic actinomycetes in controlling BLB using in planta-in vitro approaches, to characterize and identify the selected endophytic actinomycetes as well as to confirm their colonization in rice plant tissue. To obtain the objectives, the study was divided into three steps: (1) to evaluate the ability of endophytic actinomycetes in controlling BLB based on in planta (field and the greenhouse) experiments, (2) to study the biological control characters of endophytic actinomycetes using in vitro approach, (3) to characterize and identify the selected endophytic actinomycetes and their colonization in rice plant tissue. The field experiments were conducted in dry and wet seasons. The results showed that indigenous endophytic actinomycetes PS4-16 applied by seed coating and soaking techniques suppressed natural infection of BLB during dry and wet season experiments.Area under disease progress curve (AUDPC) values of PS4-16 in dry season and wet season were 1458 and 1923 respectively. Those AUDPC values were significantly different to negative control but no significantly different to the application of sinthetic bactericide. The application of endophytic actinomycetes PS4-16 under dry season could increased rice yield by 17% compared to positive control. The results of green house experiment showed that inoculation of endophytic actinomycetes AB131-1 on rice var. IR64 had a better growth than PS4-16 (21,8%). Endophytic actinomycetes AB131-1 inhibited the BLB better than PS4-16. Based on an in vitro mechanism study, all of the actinomycetes examined showed antibiosis activity against Xoo patotype IV and had a broad antimicrobial spectrum against several Gram positive and negative bacteria as well as inhibited fungal pathogens. Based on their different colony morphology observation, which produced aerial myselia and had spiral spore forming observed under both light and Scanning Electron Microscope, the selected endophytic actinomycetes AB131-1, AB131-2, PS4-16 and LBR02 belonged to the genus Streptomyces spp. The 16S rDNA sequence of AB131-1 showed 89% closed relationship with Streptomyces sp. The AB131-1, AB131-2, PS4-16 and LBR02 were able to colonize rice plant tissue which confirming them as endophytes.
Keyword: 

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