Judul: Induksi Kalus Jeruk Siam Triploid dan Transformasi Genetik pada Jeruk Siam (Citrus nobilis L.).
Abstrak: This study aims to obtain the best medium composition for callus induction of triploid tangerine from different kind of explant and regeneration of transformant citrus callus. This study is divided into 3 activities. The first aimed to induce embryogenic callus of triploid tangerine with explant from internodes, nodes, and leaves isolated from in vitro triploid tangerine buds. The explants were cultured in medium MS + MW vitamins + EM 500 mgL-1suplemented with BA 1 mgL-1, 2 mgL-1 and 3 mgL-1. The second, to introduce the gene constructs containing a selection marker (gus gene and kanamycin antibiotic) vector A. tumefaciens to triploid tangerine embryogenic callus. The third, to regenerate embryogenic callus transformant candidates in several formulations of regeneration medium. Transformant callus grown on media containing MS vitamins and MW with the addition of organic matter EM 500 mgL-1 and 10; 20; and 30% of coconut milk. Transformant callus that have been through the proliferation is regenerated on MS medium with a combination of Plant Growth Regulator:0.01 mgL-1IAA, 0.01 mgL-1 BA, 0.01 mgL-1 TDZ and 0.01 mgL-1 Kinetin. The results showed that the optimal concentration of BA for callus induction was 3 mgL-1, while different types of explants not give different results. Frequention of antibiotics application to sterilized the A. tumefaciens bacteria from callus showed the best results when done everyday. The best callus growth results of transformant callus occurs in medium MS containing vitamin MW with the addition of organic material EM 500 mgL-1. The combination of medium used for regeneration of transformant tangerine callus has not succesful yet in regenerating callus into planlet.
Keyword: Antibiotics, BA concentration, medium composition, organic matter, vitamins

Judul: Induction of genetic variability through gamma rays irradiation on embryogenic callus derived protoplast of tangerine cv. siam
Abstrak: Tangerine cv. Siam has sweet flavor, easily peeled skin, soft and juicy flesh. However, it has relatively many seeds (15-20 seeds per fruit), so it can not be competed with citrus from other countries. Fruit quality improvement of citrus has been the subject of citrus breeding program. The first step of breeding program is to increase variability, in order to efficient the selection process. Callus derived protoplast which sub cultured several years has a level of variability. The objective of this research was to increase variation of Tangerine cv. Siam through gamma irradiation on callus derived protoplast. Callus was exposed to gamma irradiation at 0, 10, 20, 30, 40, 50, 60, 70, 80, 90 and 100 Gray. Observation on the growth of callus four weeks after irradiation showed variation on morphology and weight of callus. At low doses (10-50 Gray) callus growth were not inhibited, but at high doses (60-100 Gray) callus growth were inhibited. The result of radio sensitivity dose analyzed by Curve Expert 1.4 software was 53.25 Gray. Callus regeneration ability (somatic embryo maturation and germination) were very diverse between irradiated and non-irradiated callus. Gamma irradiation affects the formation of somatic embryos. After four weeks on MW (Morel-Wetmore) medium containing 0.5 mg/l ABA, 50 Gray callus produced more somatic embryos than other doses. After four weeks on MW medium containing 0.5 mg/l GA3, only 75.9% somatic embryos from 50 Gray callus could germinate, less than other doses. All somatic embryos from non-irradiated callus could germinate. The germination of somatic embryos produced 72 regenerated plantlets. Dendogram based on morphological observations of 0 Gray regenerated plantlets showed 40% variability, while of 50 Gray were 47% and that of 60 Gray were 46%. Ten regenerated plantlets were chosen based on its variability and growth (P-2, P-8, 50-4, 50-6, 50-15, 50-24, 60-8, 60-10, 60-11 and 60-23). Dendogram based on morphological observation between 10 regenerated plantlets showed 30% variation. Molecular analysis of the 10 regenerated plantlets using three ISSR primers (ISSR-1, ISSR-2 and ISSR-4) produced 17 bands with nine polymorphic bands (52.94%). Dendogram based on molecular analysis between 10 regenerated plantlets and wild type shoots showed 22% genetic variation. In vitro and ex vitro grafting between regenerated plantlets and JC rootstock could accelerate optimal growth of plantlets. Application of ex vitro grafting was more efficient than in vitro grafting. Ex vitro grafting did not need acclimatization stage, where as in vitro grafting still need acclimatization stage before transfer to soil.
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Judul: Approximation of the Median of Poisson Distribution Using the Relation of Poisson-Gamma Distribution
Abstrak: A major drawback of median is that median cannot usually be defined in closed form, even in the cases where their distribution functions are known. This study gives an approximation of the closed form for the median of the Poisson distribution by using the relation of Poisson-Gamma distribution. The approximation uses elementary techniques based on the monotonicity of certain sequences involving tail probabilities of the Poisson distribution and the Central Limit Theorem. Furthermore, a closed form expression for the mean absolute deviation 􀜧|􀜰􀰒 􀵆 􀜯􀝁􀝀􁈺􀜰􀰒􁈻| is also studied. The median is relevant because of the fact that it minimizes the mean absolute deviation of a Poisson random variable (􀜰􀰒􁈻 by considering median as central tendency.
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