Judul: Role of Arbusccular mycorrhizal fungi and mycorrhizal endosymbiotic bacteria in increasing oil palm (Elaeis guineensis Jacq) seedlings adaptation towards biotic stress of fungal pathogen ganoderma boninense Pat.
Abstrak: Basal stem rot caused by Ganoderma boninense is the most serious disease of oil palm (Elaeis guineensis) in Indonesia and it has caused major loss in palm oil production. Under natural conditions, oil palm is often colonized by arbuscular mycorrhizal (AM) fungi and together with mycorrhizosphere bacteria offer possible advantages in increasing plant adaptation against biotic stress of pathogen. This research comprised five interrelated experiments, namely: (1) Exploration, Isolation and Identification of Arbuscular Mycorrhizal Fungi (AMF) and Mycorrhizal Endosymbiotic Bacteria from Oil Palm Rhizosphere and Their Ability in Inducing Oil Palm Adaptation Towards Biotic Stress of Pathogen Ganoderma boninense Pat; (2) Selection of Mycorrhizal Endosymbiotic Bacteria on Spores Germination of AMF Gigaspora margarita and Their Inhibition Towards Fungal Pathogen G. boninense Pat; (3) Identification of Active Compounds from Mycorrhizal Endosymbiotic Bacteria B. subtilis B10 that Inhibit the Growth of Fungal Pathogen G. boninense Pat; (4) Adaptation of Oil Palm Seedlings Inoculated with AMF and Mycorrhizal Endosymbiotic Bacteria B. subtilis B10 Towards Biotic Stress of Pathogen G. boninense Pat; (5) Analyzing the Response of Oil Palm Seedlings Inoculated with AMF and Mycorrhizal Endosymbiotic Bacteria in the Form of Active Compound Profile as Expression of Oil Palm Adaptation Towards Biotic Stress of Pathogen G. boninense Pat. The soil sampels were used in this experiment came from Aek Pancur Plantation belong to Indonesian Oil Palm Research Institute, Medan. The results showed that twenty isolates of mycorrhizal endosymbiotic bacteria were obtained from spores of AMF isolated from oil palm rhizosphere and were dominated by genus of Bacillus sp. Among these isolates, isolate B10 identified based on 16S rDNA as Bacillus subtilis B10, had the highest activity against G. boninense in vitro by producing intracellular active compounds with molecular weight 255.39 and postulated as of 2-(4-aminophenoxy)-6-methyl-tetrahydro-2H-pyran-3,4,5- triol. Dual inoculation of AMF and B. subtilis B10 on oil palm seedlings resulted in the lowest basal stem rot disease incidence caused by G. boninese which indicated disease severity index was only 5% and necrotic area of roots just 10%. Application of AMF together with B. subtilis B10 also increased oil palm seedlings height, root dry weight and stem diameter at 52 weeks after planting. The adsorption of nitrogen (N), phosphorus (P), potassium (K) and magnesium (Mg) increased when seedlings were co-inoculated with AMF and bacteria B. subtilis B10 together. This finding is important in terms of recommendation for application of AMF and bacteria B. subtilis B10 as biocontrol of pathogen G. boninense causal agent of basal stem rot in oil palm.
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Judul: Peran bakteri kitinolitik dan fungi mikoriza arbuskular dalam pengendalian busuk pangkal batang kelapa sawit
Abstrak: Basal stem rot (BSR) is the most serious disease of palm oil that caused by Ganoderma boninense Pat. The objectives of these researches were to find chitinase-producing bacterial which inhibit G.boninense growth and to determine the relationship between mycorrhizal and chitinolytic bacterial in controlling the BSR. The experimenthals were conducted in laboratory, secreen house dan fields. The research activities were: (i) exploration of chitinolytic bacterial as antagonistic agents of pathogens (ii) evaluate the pathogenicity, index chitinolitic of the chitinolytic bacterial and their antagonism effect against G. boninense, (iii) study on the application of chitinolytic bacterial and AMF in controlling the oil palm BSR through split plot experimenthal design. There were seven isolate B13, B14, B16, B42, Al11, TB41 and L34 have been selected as the best chitinolase-producing bacterial and they were not pathogenic to plants. The study showed that selected bacterial have differences on chitinolytic index. All of them suppressed the growth of G. boninense above 95% in vitro antagonism test using dual culture method on liquid media. However the antagonism test on PDA only isolate of AL11, TB41 and L34 had higher antagonism capacity against the pathogen. The severity of basal stem rot that expressed by the root necrotics were reducted since the oil palm seedling showed high degrees of mycorrhizal root colonization. The application of combination of chitinolytic bacterial and AMF suppressed the disease severity (95%) higher compare to the single one (55% - 7
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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