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: Efikasi Bakteri Endofit dan Plant Growth Promoting Rhizobacteria dalam Menekan Perkembangan Penyakit Layu Bakteri (Ralstonia solanacearum) pada Tomat
Abstrak: Tomato (Lycopersicum esculentum Mill.) is a popular vegetable in Indonesia, but the production levels are still fluctuated. One of the factors affected productivity is the incidence of bacterial wilt disease caused by Ralstonia solanacearum. Effective control to manage the disease which is environmentally friendly is the use of biocontrol agents. Application of endophytic bacterial (Staphylococcus epidermidis BC4) and Plant Growth Promoting Rizhobacteria (Pseudomonas fluorescens RH4003 and Bacillus subtilis AB89) as biocontrol of tomato bacterial wilt was expected to be an alternative tool. The objective of this study is to determine the efficacy of combination among endophytic bacteria and PGPR to suppress the development of bacterial wilt disease (R. solanacearum) and promote the growth of tomato. Depend on the growth test (growth rate and dry weight plant), the combination of bacteria that could promote the growth of tomato plant was combination of S. epidermidis BC4 75% with P.fluorescens RH4003 25%. That combination gave a better effect than the other treatments and control, but did not provide better suppression than treatment of single bacterium. Based on sinergism test, the relationship between PGPR and endophytic bacteria was an antagonistic. However, there were combination treatments which were able to suppress the disease, ie. combination of S. epidermidis BC4 50% with P. fluorescens RH4003 50% and the combination of S. epidermidis BC4 50% with B. subtilis AB89 50%.
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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