Judul: Pemanfaatan Streptomyces spp. sebagai Agen Pengendali Hayati Mikrob Patogen pada Tanaman Tomat (Solanum lycopersicum)
Abstrak: Streptomyces spp. is one of the bacterial antagonists, which can be used to control microbial plant pathogens. Aims of this study were to examine the ability of two Streptomyces spp. isolates (LSW05 and PS4-16) in reducing tomato diseases in field and to obtain an effective application method. Both isolates were applied singly and in combination using three application methods (seed coating, soil drenching and spraying). Streptomyces spp. effectively suppressed disease severity, increased plant height, dry weight, fruit weight and fruit number per plant. LSW05 isolate applied as soil drenching suppressed disease severity by lowering the Area Under Disease Progress Curve (AUDPC) value up to 24% and increased the plant dry weight up to 187.10%. On the other hand, LSW05 isolate applied as seed coating improved plant height as measured by Area Under Height Growth Curve (AUHGC) up to 47.5% and increased fruit weight (794 g/plant) and fruit number (14,3 fruit/plant) as compared with control. Seed coating with Streptomyces LSW05 gave the highest benefit compared to the other treatments and non treatment up to Rp 75.244.600/ha. The results of this study provide a good prospect of Streptomyces based biocontrol agent to be applied to organic farming system.
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Judul: The Potency of Streptomyces spp. as Biocontrol Agent of Soil Borne Fungi Sclerotium rolfsii through In Vitro and In Planta Assay in Tomato Plant (Solanum lycopersicum).
Abstrak: Selected indigenous isolates of Streptomyces spp. are known as source of antimicrobial compound. The research aims to study the ability of isolates of Streptomyces spp. and their application in suppressing the growth of Sclerotium rolfsii in vitro and in planta assay in tomato plant. Six indigenous Streptomyces spp. isolates which have been isolated from soil rhizhosphere that able to inhibit various soil borne microbial pathogen were chosen against Sclerotium rolfsii in vitro and in planta assay in tomato plants. In vitro assay showed that LSW 05 and PS 4-16 inhibited the growth of Sclerotium rolfsii by 84 and 33% respectively and they were selected for in planta assay. Pouring application of Streptomyces could suppressed the disease level and arised the height of tomato plant, but it not increased percentage of tomato seed germination if it compare to seedcoating application on tomato plant with S. rolfsii addition. LSW 05 isolate could supressed of area under the disease progress curve (AUDPC) until -906. The isolate also increased the height of tomato plant which had the higest value of area under the length progress curve (AULPC) (118) and percentage of tomato seed germination by 70% on S. rolfsii addition. Based on this capability, the LSW 05 isolate is potential to be developed as a biological control agent for soil microbial pathogens in tomato plant. Key words: Streptomyces spp., biocontrol, Sclerotium rolfsii, tomato plant
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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