Judul: Penapisan Rizobakteria Toleran Kekeringan Pemacu Tumbuh Tanaman Kedelai dan Aplikasinya di Rumah Kaca
Abstrak: Drought stress can reduce the productivity of crops. Therefore, strategies to promote growth of plants that can grow well in drought conditions is required. One of the way is by using the plant growth promoting rhizobacteria (PGPR). The aim of this study was to screen rhizobacteria in drought stress and apply them on soybean in greenhouse. A total of 27 rhizobacteria consisted of 14 Pseudomonas sp. (Crb), 11 Bacillus sp. (Cr), and 2 Bradyrhizobium japonicum. (Bj) was screened on drought conditions using media supplemented with Polythylene Glycol (PEG) 6000 then quantitatively tested for exopolysaccharide product. Selected bacteria were tested for antagonistic assay tested before combining them in a package formula in the peat. Bacteria were grown in media skim milk and molasses then inoculated into 50 g of peat soil. The formula were tested for the viability and effectiveness on soybeans in green house. Total of 17 bacteria were successfully screened and all grow well at low osmotic potential (-2 Mpa) medium and produced exopolysaccharide ranging 1.7-8.0 mg/ml. Based on the exopolysaccharide produced and antagonist test, five packages of formula were selected. Viability of five formulas were stable until the three months of storage period. Application of the formulas for soybean in green house, formula F4 showed significant effect on plant height, shoot and root fresh weight and root dry weight in both wet and dry conditions.
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Judul: Karakterisasi Rizobakteria Pemacu Tumbuh Tanaman dan Toleran Kekeringan
Abstrak: Plant Growth Promoting Rhizobacteria (PGPR) are a group of bacteria that have some ability to support plant growth. Two of those rhizobacteria are Bacillus and Pseudomonas. This study aimed to isolate and characterize indigenous rhizobacteria Bacillus and Pseudomonas isolated from soybean (Glycine max) rhizosphere from Nusa Tenggara Barat. Characterization included the ability to stimulate soybean sprouts growth, indole acetic acid (IAA) production, the ability to face drought stress, phosphate solubilizing ability, and chitinase enzyme production. There were 22 isolates of Pseudomonas and 29 of Bacillus were isolated using selective media King's B and NB. Sixteen isolates consisting seven Pseudomonas and nine Bacillus isolates could significantly stimulate soybean sprouts growth. With the addition of 0.2 mM tryptophan in liquid media, bacteria are able to produce IAA in the concentration range of 1.02 to 21.06 ppm for genus Pseudomonas and 4.59 to 5.44 ppm for genus Bacillus. The sixteen isolates were tested for their ability in facing drought stress, phosphate solubilizing, and chitinase enzymes production. Isolates pntb80 and bntb20 can survive up to -2.5 MPa osmotic pressure on the media with PEG 6000 added as osmotic pressure controller. The highest phosphate solubilizing index were shown by pntb18 on Pikovskaya agar with tricalcium phosphate. The highest chitinolytic index were shown by bntb22 on 1% chitin media.
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Judul: Cycle Hamilton pada Graf Lengkap, Graf Regular, dan Graf 2-Connected 4-Regular Berorder Kurang dari Sepuluh
Abstrak: Suatu graf disebut graf Hamilton apabila graf tersebut memuat cycle Hamilton, yaitu cycle yang melewati setiap vertex tepat satu kali. Menentukan keberadaan cycle Hamilton pada suatu graf dapat menggunakan syarat cukup yang berupa teorema-teorema yang telah diperkenalkan sejak tahun 1950-an. Beberapa syarat cukup yang dibahas dalam karya ilmiah ini adalah syarat cukup yang berhubungan dengan graf lengkap dan graf regular. Suatu graf lengkap berorder 𝑛������ ≥ 3 dan graf r-regular berorder 𝑛������ ≤ 2𝑟������ + 1 merupakan graf Hamilton, Karena kedua graf tersebut memuat cycle Hamilton. Selanjutnya, syarat cukup tersebut digunakan untuk menentukan keberadaan cycle Hamilton pada graf 2-connected 4- regular berorder kurang dari 10.
Keyword: graf Hamilton, graf regular, graf lengkap, graf 2-connected 4-regular