Judul: Development of White Root Fungal Disease (Rigidiporus microporus) in the Galang Deli Serdang Rubber Plantation Ecosystem, North Sumatra
Abstrak: WIDYA MINATI. Development of white root fungi (Rigidoporus microporus) Rubber Plantation in Galang, Deli Serdang, North Sumatera. Supervised by BONNY PUTRA WAHYU SOEKARNO and ACHMAD. White root diseases (WRD) inducing by Rigidoporus microporus pathogen is one of the crucial diseases in rubber plantations. It can degrade harvest production in a range of 3 to 15 %. Becoming one of the soil-borne diseases, it has a strong relationship with the rubber plantation ecosystem. The R. microporus pathogen is highly affected by the ecosystem condition. The variation of disease severity in plantations occurred differently in each plantation as ecosystem alteration shapes, making research regarding the WRD development on the rubber plantation was needed to be carried out. This research used a survey method. It was conducted from January to March 2019 at three rubber plantations namely the PTPN III, and two smallholder estates situating at Galang Sub-district, Deli Serdang- North Sumatera. The chemical-soil analysis was taken in the North Sumatera Soil Laboratory of BPTP (Balai Penelitian Tanah). The laboratory-analysis of soil compounds consisted of organic-C, N, P, K, C/N ratio, and pH. Climate and vegetation data were also then investigated. The link between disease severity and soil chemicals was correlated to seek their relationship. Field observations indicate that the WRD attacks happen in all sampling plantations. This is due to the remaining plants found in each sampling plantation becoming the inoculum sources of the WRD. The highest and lowest attacks of WRD occurs on the first and second month accordingly in the PTPN III plantation at sampling plantations of A3 (47% and 53%), and small-holder estates (5% and 5%), respectively. Furthermore, the disease severities also happen in the same plantations namely at plantation A3 of PTPN III on both months (32.5% and 34.2%) and small-holder estates on both months (5% and 5%). The high attack and severity of the disease in the A3 plantation is presumed to cause by the soil containing highly sandy texture generating a high porosity as well. A high porosity supplies enough oxygen for the R. microporus to develop. Furthermore, a high humidity condition in this sampling plantation is designated by the weed vegetation of Nephrolepis bisarrata helping the WRD developed optimally. The correlation analysis between soil chemical compound and the disease severity indicates that the phosphate content and C/N ratio contribute a significant influence in a negative direction. The organic material compound level and nutrients denote an indirect role in the disease development namely providing nutrients for the plant. The lower contents of the C/N ratio and phosphate demonstrates the higher severity level of WRD. This research can be inferred that the development of WRD in the research location is surmised affecting by a high micro-humidity, nutrient compounds, and low organic material on the soil as well as a soil texture with high porosity. Keywords: climate, disease severity, soil chemical, rubber plantation, Penyakit jamur akar putih (JAP) yang disebabkan oleh patogen Rigidoporus microporus merupakan salah satu penyakit penting pada perkebunan karet. Kerugian yang ditimbulkan oleh penyakit ini dapat menurunkan produksi antara 3 -15% terutama di perkebunan rakyat. Sebagai salah
Keyword: Iklim, keparahahan penyakit, kimia tanah, pertanaman karet, pertanaman karet, climate, disease severity, soil chemical, rubber plantation

Judul: Potensi Trichoderma harzianum dan Mikoriza untuk Pengendalian Penyakit Jamur Akar Putih (Rigidoporus lignosus (Kloztch) Imazeki) pada Karet.
Abstrak: Indonesia is the largest producer of rubber after Thailand. The development of the rubber industry is still on going. However, the presence of rubber diseases become a problem in the rubber industry development. White root fungus disease caused by the fungus Rigidoporus lignosus is a major disease in rubber plantations. The experiment aims to determine the potential of the fungus Trichoderma harzianum and mycorrhizae fungi for controlling white root disease on rubber seedlings in the greenhouse. The experiment has been done in complete randomizeddesign, 8 treatments and 4 replications. The treatments were, applications of T. harzianum, mycorrhizae, and their combinations, with and without R. lignosus. The result have shown that T. harzianum, mycorrhizae, and their combinations have supressed JAP diseases incidence and severity. At the time of seedlings, the treatment of T. harzianum singly has found as the most effective and efficient in supressing diseases severity and in increasing plant vegetative growth.
Keyword: mycorrhiza, Rigidoporus lignosus, rubber, Trichoderma harzianum

Judul: Penggunaan Teorema Homeomorphy 2-Manifold dan Teorema Euler Poincare pada Torus 𝑇�� dan Simplicial Complex 𝐾��
Abstrak: Two dimensional topological spaces are said to be homeomorphic if they have the same topological invariant, where one of topological invariant used is an Euler characteristic. Homeomorphy 2-Manifold’s Theorem and Euler Poincare’s Theorem are used to distinguish two topological spaces. Homeomorphy 2-Manifold’s Theorem uses Euler characteristic to identify two dimensional topological spaces. Euler Poincare’s Theorem is an alternative way to find Euler characteristic with Betti number, which is topological invariant as well. The objective of this paper is to investigate the homeomorphism of torus 𝑇����� and simplicial complex 𝐾�����. Topological space torus and simplicial complex 𝐾����� have the same Euler characteristic, which is two. Based on Homeomorphy 2-Manifold’s Theorem topological space torus 𝑇����� and simplicial complex 𝐾����� is homeomorphic.
Keyword: simplicial, torus, Euler, homeomorphism, topology