Judul: Rhizobacteria of Bacillus sp. and Pseudomonas sp. growth promoter drought tolerant and their application on maize
Abstrak: Agricultural land in Indonesia was largely dominated by untapped dry land. Maize (Zea mays L.) is one of the staple crops that are known could be cultivated on dry land. The future of agricultural development strategy oriented to the application of biological fertilizers and optimize ecological function of each ecosystem component. Rhizosphere has been known to contain microorganisms that can improve the plant growth, both directly and indirectly. Those rhizobacteria was known as plant growth promoting rhizobacteria (PGPR), include genus of Bacillus and Pseudomonas. Rhizobacteria had adapted to drought conditions, one way by producing exopolysaccharide (EPS). Therefore, this research was aimed to screening of rhizobacteria of Bacillus and Pseudomonas drought tolerant as growth promoter of maize growth. Utilized of rhizobacteria could be alternative way that are effective and environmental friendly. Screening in vitro of rhizobacteria as growth promoter of 47 Bacillus CR and 34 Pseudomonas CRB resulted 24 and 9 isolates were able to stimulate the growth of maize sprouts, significantly. Further screening of those growth promoter of the rhizobacterial isolates to drought tolerance with PEG 6000 resulted 7 isolates of Bacillus CR and 6 isolates of Pseudomonas CRB that were able to grow on medium with osmotic pressure -1 MPa and -2 MPa, respectively. Rhizobacterial isolates of growth promoter and drought tolerance were tested for antagonist mechanisms which aims to determine ability to live together in one medium if to be made formulation. Both non antagonist rhizobacterial isolates were evaluated for their potential in producing EPS by Dubois method. CRB 19 and CR 90 exhibited the highest activity of EPS production up to 0.346 mg mL-1 on medium with -2.0 MPa and 0.107 mg mL-1 on medium with -0.73 MPa, respectively. Based on 16S rRNA sequence analysis revealed that CRB 19 and CR 90 belonged to Pseudomonas aeruginosa strain B2 and Brevibacillus brevis B33, respectively. Four of potential isolates of each genus to be made formulation using peat soil as carrier material (F1, F2, F3 and F4). In addition, CRB 19 and CR 90 as selected isolates of each genus also to be formulated. Formulation were selected based on the highest of OD and EPS value. Rhizobacterial formula were further applied in planta in greenhouse using a completely randomized design with two factors (water content and formula). Water content consists of two levels (field capacity and under of field capacity), and the formula consists of seven levels (six formulas+control). In planta test showed that formula CRB 19 and F3 (CR 83+CRB 10) were the best formula that could enhance plant growth parameters compared to other formula. Furthermore, those drought tolerant rhizobacteria had potency to be developed as inoculants of maize planted in dry land agriculture.
Keyword: growth promoter, rhizobacteria, maize, drought tolerant

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: 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