Judul: Keanekaragaman Cendawan Mikoriza Arbuskula (CMA) di Hutan Pantai Ujung Genteng, Sukabumi-Jawa Barat
Abstrak: Indonesia is one of the countries that has a megadiversity of microorganisms and has a large area of coastal forests. However, research on microbial diversity particularly AMF as one of the dominant microbes in a coastal forest ecosystems has not been done extensively. The main objective of this research was to study the diversity and distribution of AMF in coastal forest and to analyse effects of salinity on the fungal and plant community at Coastal Forest Ujung Genteng Cape, Sukabumi - West Java. This research was carried out in two parts: field, green house and laboratorium experimental activities. Field experimental activities were conducted for vegetation analysis, collecting of plant root system, rhizosphere soils from tree and pole phase,. seedling of understorey plants for fungal colonization analysis, isolation and identification of AMF and soil characteristics, include salinity. Green house and laboratorium activities were carried out for isolation, identification and colonization analysis of AMF. Field research location was divided into three zones, first zone was 0 – 70 m distance from coastal area (P), second zone was 71 – 140 m distance from coastal area (T), and third zone was 141 m distance from coastal until forest up to area in the center (H). Twenty three AMF species from 45 plant rizosphere were identified. The fungi belong to 5 species of Acaulospora, 2 species of Gigaspora, 13 species of Glomus, 1 species of Paraglomus and 2 species of Scutellospora. Glomus geosporum was the most dominant AMF in the ecosystem with the value of frequency was 16.49% - 23.67%. Glomus etunicatum, Acaulospora foveata, A. longula, A. scrobiculata, A. tuberculata, and Scutellospora auriglobosa were the AMF that had frequency higher than other species but less than G. geosporum in the field. Results from vegetation analysis indicated that Ujung Genteng Coastal Forest had 68 plant species belonging to 40 families. Dysoxylum parasiticum and Piper cf. baccatum were dominant plants in the ecosystem. The plant community measured at the three zones experimental sites were differed. The similarity index value of the plant community (Is) between coastal P) and center (T) area was 35.42%, between center (T) and forest center (H) was 32.53%, and between coastal edge (P) and forest center (H) was 27.04%. There was no correlation between diversity of plant and diversity of AMF onserved. Diversity of AMF were influenced with all interaction environment factors especially salinity. Two species of AMF had a narrow distribution and found only in a rhizosphere of one plant species . Glomus sp 5. found only in Guettarda speciosa rhizosphere and Glomus sp6. in Salacia sp. rhizosphere. Nineteen species were identified from P zone, 17 species from T zone and 14 species from H zone, with the index diversity values of AMF were 0.73 – 6.64, 0.85 – 4.93 and 1.26 – 4.84, respectively. The salinity at Ujung Genteng Cape was falled in moderate degree with the value of 420 – 1735 μs/cm. The salinity influenced the diversity of AMF and plant community structures. Nineteen species were identified from P zone, 17 species from T zone and 14 species from H zone,
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Judul: Diversity and Colonization of Arbuscular Mycorrhizal Fungi (AMF) in Trapping Culture Martabe, North Sumatra
Abstrak: Cendawan Mikoriza Arbuskula (CMA) adalah kelompok cendawan mikoriza yang bersimbiosis secara mutualisme dengan akar tanaman. Studi mengenai keanekaragaman CMA pada ekosistem hutan di wilayah tropis Indonesia masih terbatas dan eksplorasi CMA secara langsung dari rizosfer alami sering diperoleh hasil yang relatif rendah. Penelitian ini bertujuan mendapatkan informasi mengenai keragaman dan kolonisasi CMA pada rizosfer hutan Martabe, Sumatra Utara melalui kultur trapping. Penelitian dilakukan dengan membuat kultur trapping menggunakan tanaman Sorghum vulgare dan Mucuna bracteata masing-masing sebanyak 3 ulangan. Keragaman spesies CMA diketahui dengan mengisolasi dan mengidentifikasi spora berdasarkan karakteristik morfologi kemudian dilakukan penghitungan persentase kolonisasi. Sebanyak 18 spesies CMA berhasil diperoleh yang terdiri dari genus Glomus, Gigaspora, dan Acaulospora. Keragaman spesies CMA didominasi oleh genus Glomus. Jumlah spesies CMA tertinggi ditemukan pada tanaman Mucuna bracteata sedangkan jumlah spora terbanyak ditemukan pada tanaman Sorghum vulgare. Persentase kolonisasi CMA pada akar tanaman Sorghum vulgare dan Mucuna bracteata masing-masing sebesar 42,81% dan 51,06% yang ditandai dengan terdapatnya struktur berupa arbuskula, hifa eksternal dan internal, titik penetrasi serta vesikula. Kedua jenis tanaman tersebut termasuk dalam tanaman adaptif yang dapat bersimbiosis dengan CMA., Arbuscular Mycorrhizal Fungi (AMF) is a mutualism symbiosis between mycorrhizal fungi and plant roots. Studies of AMF diversity in Indonesian tropical forests still need to be expanded, and exploration of AMF directly from the natural rhizosphere often has relatively low results. This study aims to obtain information on the diversity and colonization of AMF in forest rhizosphere Martabe, North Sumatra, through trapping culture. The research was carried out by making trapping cultures using Sorghum vulgare and Mucuna bracteata plants with three replications each. The diversity of AMF species is known by isolating and identifying the spores based on morphological characteristics and then calculating the percentage of colonization. A total of 18 AMF species were obtained, consisting of genera Glomus, Gigaspora, and Acaulospora. The species diversity of CMA is dominated by the genera Glomus. The highest number of AMF species was found in Mucuna bracteata, while the highest number of spores was found in Sorghum vulgare. The percentage of AMF colonization on Sorghum vulgare and Mucuna bracteata was 42.81% and 51.06%, indicated by the presence of arbuscules, external and internal hyphae, penetration points, and vesicles. Both types of plants are included in adaptive plants that can be in symbiosis with AMF.
Keyword: Akar, Hutan, Indonesia, Rizosfer, Spora, Forests, Indonesian, Rhizosphere, Roots, Spores

Judul: Truncated Stop Loss as a Optimal Solution of Reinsurance Agreement in One-Period Model
Abstrak: Reinsurance is one of risk management efforts of an insurance company, which is called the cedent. Similar with insurance, reinsurance constitutes the cedent to pay the premium. We consider one-period reinsurance model and derive a rule which minimizes the ruin probability of the cedent for a fixed reinsurance premium. Therefore, it is needed to construct an optimal reinsurance agreement for the cedent. The premium is calculated according to four different principles, i.e. economic, generalized zero-utility, Esscher, and mean-variance principles. Stop loss is a reinsurance contract which protect the insurance company for losses that exceed a certain amount. The result of this research shows that a truncated stop loss is an optimal agreement in the class of all reinsurance contracts with various premiums calculated using above mentioned principles.
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