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"Microbial communities usually have mixed populations, only in uniqueenvironmental situations do microorganisms live entirely alone. Thus many types of interactions are possible among the members of an ecosystem?s community. In general, the constant association of different organisms in an ecosystem is referred to as symbiosis, with the associates being called symbionts. One type of a symbiosis is antagonism. Antagonism is a symbiotic relationship in whichone population of microorganisms has a harmful effect on the growth of another microbial population (Batzing 2002: 696). A number of microorganisms (bacteria, yeasts, fungi) which effectivelycontrol postharvest pathogens have been identified as antagonists (Mari and Guizzardi 1998:60). A variety of microbial antagonists were reported to control several different pathogens on various fruits. The organism that suppresses the pest or pathogen is referred to as the biological control agent (BCA) (Pal & Mcspadden Gardener 2006: 1). Biological control may in simple terms be defined as the use of one living organism to control another (Druvefors 2004: 4).Often antagonists are isolated on the surface of plants; this natural presence makes them more likely to succeed because of their colonization ability and environmental adaptation (Mari and Guizzardi 1998:60). The use of yeasts as antagonists appears to be quite promising, although the mechanism has not yet been fully elucidated. Some antagonist yeasts have been reported as biocontrol agent of fungal pathogen on fruits. Zhao et al. (2008: 115--116) reported that tomato fruit treated with Pichia guillermondii had an infection rate of 25% which was caused by Rhizopus nigricans, which wassignificantly lower than the control (41.67%). Kalogiannis et al. (2006: 72) reported that Rhodotorula glutinis Y-44 significantly reduced disease incidence caused by Botrytis cinerea on tomato by 52%, compared to the untreated control. Zhang et al. (2004: 84) reported that the application of Cryptococcus laurentii resulted in low average decay incidence caused by B. cinerea in fruit by 7.1%, compared with 40% in the water-treated control fruit. University of Indonesia Culture Collection (UICC) collected epiphytic yeasts from plant samples of Cibodas Botanical Garden, and moulds from decayed tomatoes and infected plants. The ability of the epiphytic yeasts as biocontrol agents against tomato spoilage-causing moulds has not beenreported. This study consists of two parts. Part 1 is The Antagonistic Ability of Epiphytic Yeasts of Cibodas Botanical Garden on Tomato Plant Infected-Causing Moulds. Part 2 is The Potential of Candida sp. UICC Y-328 as a Biocontrol Agent of Aspergillus ochraceus on Postharvest Tomatoes.The purposes of this study were to investigate the ability of six species of epiphytic yeasts in inhibiting the growth of tomato plant infected-causing moulds, and the potential of Candida sp. UICC Y-328 as a biocontrol agent in reducing postharvest tomato spoilage caused by Asp. ochraceus. The media used for growing the yeasts was Yeast Malt Agar (YMA), and maintenance for fungi was Potato Dextose Agar (PDA). The media used for antagonistic test were PDA and Potato Dextrose Broth (PDB). Antagonistic test by strip method was carried out by using the concentrations of yeast cells at (0.7--4.45) x 108 CFU/ml, and Asp. ochraceus at (7.0--8.1) x 107 CFU/ml, Asp. terreus Thom at (7.7--8.6) x 107 CFU/ml andDrechslera sp. at (0.45--3.5) x 105 CFU/ml. The yeast cells were inoculated 4 hours earlier before inoculation of mould spores on PDA in Petri dishes. Results showed that Candida sp. UICC Y-328 has highest percentage of colony reduction of Asp. ochraceus (56.45%), followed by Metschnikowia reukaufii UICC Y-351 on reducing colonies of Asp. terreus and Drechslera sp. (25.42% and 51.28%, respectively) during 6-day incubation. Antagonistic test by co-culture method was carried out by using the concentrations of yeast cells at (0.7--4.45) x 108 CFU/ml, and Asp. ochraceus at (6.0--8.6) x 107 CFU/ml, Asp. terreus at (4.6--9.5) x 107 CFU/ml. The yeast cells were inoculated 8 hours earlier before inoculation of mould spores on PDB. Results showed that Candida sp. UICC Y-328 reduced the size of conidial heads(5.52%) and hyphae (8.29%) of Asp. ochraceus, at 3-day incubation.Cryptococcus laurentii UICC Y-379 reduced the size of conidial heads and hyphae of Asp. ochraceus (15.07% and 11.60% respectively) and Asp.terreus (12.35% and 24.47% respectively) at 3-day incubation. Antagonistic test by slide culture method showed that the yeast cells of four strains (Candida rancensis UICC Y-326, Cr. laurentii UICC Y-319, Cr. laurentii UICC Y-379,and M. reukaufii UICC Y-351) attached to hyphae of Drechslera sp. after 3- and 4-day incubation.Cells of Candida sp. UICC Y-328 attached to hyphae of Drechslera sp. after 4-day incubation. Cells of Cr. laurentii UICC Y-385 was not able to attach to hyphae of Drechslera sp. Candida sp. UICC Y-328 was potential in reducing the growth of Asp. ochraceus, and was investigated further for its potential as a biocontrol agent. Wounds on postharvest tomatoes were inoculated with 25 µl of yeast cellsuspension and 25 µl of mould spore suspension. The yeast cells wereinoculated 24 hours earlier before inoculation of mould spores on wounds of tomatoes. Biocontrol study showed that incidence of spoilage in postharvest tomatoes which were wounded and inoculated with Candida sp. UICC Y-328 and Asp. ochraceus, were reduced by 20% after 15-day incubation at room temperature. All postharvest tomatoes which were wounded and inoculated with Asp. ochraceus as control, were spoiled (100%). Synthetic fungicide Dithane M-45 at a concentration of 0.08% reduced spoilage incidence by 70%. Candida sp.UICC Y-328 was not effective as biofungicide in reducing spoilage incidence."

"ABSTRACTBiological control of postharvest diseases of fruits and vegetables byantagonistic microorganism seems increasingly promising to replace the use of synthetic fungicides which are subjected to some limitation due to development of fungicides-resistant strain of the pathogens and risk for consumers and the environment (Lima et al, 1999). Several species of yeast have been reported to reduce postharvest fungal decay on fruits. One of the antagonistic yeast that has been use as commercial biocontrol is Metchnikowia fructicola in Shemerm product (Vero et al., 2002) Yeast Rhodotomla has been studied for the postharvest biologicalcontrol various mould pathogens on various fruit (Castoria et al., 1997).University of Indonesia Culture Collection (UICC) have Rhodotorula spp.strains from plants of Cibodas Botanical Garden, and moulds frompostharvest decayed-tomatoes and plants. The ability of these yeast strains as biocontrol agents against has not been reported.This thesis consists of two parts. Part 1 is entitled The antagonisticActivity of Rhodotorula spp. from Cibodas Botanical Garden Against Tomato Plant Infected-Causing Moulds. Part 2 is entitled The Potential of Rhodotorula sp. UICC Y-381 as Biocontrol Agent of Aspergillus ochraoeus on Postharvest Tomatoes. The objectives of this research are to obtain a potential Rhodotorula sp. with antagonistic activity against tomato infected-causing moulds, and to obtain infoimation on the ability of Rhodotorula sp. UICC Y- 381 as a biocontrol agent in reducing the severity of decay by Aspergillus ochraceus. The research was carried out in Laboratory of Microbiology, Department of Biology, and Center of Excellence Indigenous Biological Resources-Genome Studies (CoE IBR-GS), Faculty of Mathematics and Natural Sciences, from July 2008-July 2009.Yeast Malt Agar (YMA) was used for yeast growth medium, and PotatoDextrose Agar (PDA) was used for maintenance of fungi. The media PDA and Potato Dextrose Agar (PDB) were used for antagonistic test.Six strains of Rhodotorula spp. (Rhodotorula sp. UICC Y-318,Rhodotorula sp. UICC Y-325, Rhodotorula sp. UICC Y-332, Rhodotorula sp. UICC Y-381, Rhodotomla sp. UICC Y-384, and Rhodotorula sp. UICC Y-386) were investigated as antagonistic yeasts against Aspergillus ochraceus D1.2.2.SSM3, A. terreus D2.2.MC, and Drechslera sp. D1.3.MC. The yeasts were obtained from plants of Cibodas Botanical Garden, and the moulds were obtained from decayed tomatoes and infected plants, belonging to the University of Indonesia Culture Collection (UICC). Antagonistic test by strip method was carried out by usingconcentration of yeast cells at (1 .2-5.2) x 10° CFU/ml, and A. ochraceusD1.2.2.SSM3 at 4.7 x 10? CFU/ml, A. terreus D2.2.Mc at 3.2 x 10° CFU/ml,and Drechslera sp. D1.3.MC at 5.2 x 10? CFU/ml. Inoculation of the yeastcells on PDA was carried out 4 hours earlier before inoculation of mouldspores on petri dishes. Results showed that highest percentage reduction of mould colonies was shown by Rhodotorula sp. UICC Y- 325 againstDrechslera sp. (28.12%-72.14%), followed by Rhodotorufa sp. UlCC Y-381 against A. ochraoeus (54.28%-72.46%), and Rhodotoruta sp. Y-318 against A. terreus (21.76% - 58.10%) during 6-day incubation.Antagonistic test by co-culture method was carried out by usingconcentration of yeast cells at (1 .58-5.59) x 10° CFU/ml, and Aspergillus ochraceus D1.2.2.SSM3 at 7 x 10? cFU/ml, A. terreus D2.2.MC at 1.5 x 10? CFU/ml. Inoculation of the yeast cells on PDB was carried out 8 hours earlier before inoculation of mould spores on broth medium. Results showed that highest percentage reduction of conidial heads and hyphal width was shown by Rhodotorula sp. UICC Y-381 against A. ochraceus (9.45% and 12.43%; 7.10% and 7.51 %, after 2- and 3-day incubation, respectively). Rhodotorula sp. UICC Y-332 reduced conidial heads of A. terreus (10.17% and 9.60% after 2- and 3-day incubation) but, was not able to reduce hyphal width of A. terreus. Microscopic observation by slide culture method on PDA showed that there was attachment of Rhodotorula spp. cells to the hyphae of Drechslera sp., however, Rhodotorula spp. UICC Y-386 attached more intensively and colonized the hyphae.The ability of Rhodotorula sp. UICC Y-381, which was isolated fromplant leaves, as a biocontrol agent against postharvest tomato fruit decay- causing mould Aspergillus ochraceus D1 .2.2.SSM3 was evaluated. Observation was carried out for 15 days at 25°C - 27°C. Results showed that Rhodotorula sp. UICC Y-381 was able to reduce the severity of decay by A.ochraceus with 100% reduction until day-12, when compared to control. The synthetic fungicide Dithane M-45 at a concentration of 0.08% reduced the severity of decay to 100% until 15-day incubation."

"Penelitian telah dilakukan untuk memperoleh strain khamir penghasil mikosin yang dapat membunuh isolat-isolat khamir kontaminan santan dan produk nata de coco. Penelitian dilakukan di Laboratorium Mikrobiologi, Departemen Biologi, FMIPA-UI, Depok dari Desember 2006 - Mei 2007.Khamir-khamir yang digunakan adalah 18 strain khamir UICC dan 11 isolat khamir kontaminan santan dan produk nata de coco. Penapisan aktivitas mikosin menggunakan metode gores pada Killer Medium Agar (KMA) dengan pH 4,4 dan mengandung metilen biru. Hasil penapisan menunjukkan bahwa 18 strain khamir positif menghasilkan mikosin terhadap 11 isolat khamir kontaminan santan dan produk nata de coco. Pengujian aktivitas mikosin secara semi kuantitatif menggunakan metode sumur dan jumlah sel khamir penghasil mikosin yang digunakan adalah 1,2x108 sel/ml sedangkan jumlah sel khamir kontaminan adalah 3x107 sel/ml.Hasil pengujian menunjukkan bahwa sebanyak 14 strain khamir positif menghasilkan mikosin terhadap tiga isolat khamir kontaminan dari santan. Dua belas strain memiliki aktivitas mikosin dengan spektrum luas sedangkan dua strain memiliki aktivitas mikosin dengan spektrum sempit. Candida rancensis C. Ramirez & A.E. Gonzales UICC Y-326 dan Rhodotorula sp. F.C. Harrison UICC Y-332 menghasilkan mikosin yang paling banyak membunuh isolat-isolat khamir kontaminan dari santan dibandingkan dengan 12 strain khamir mikosinogenik lainnya."

"Informasi tentang kemampuan mikosin dari 18 strain khamir asal Kebun Raya Cibodas terhadap 10 isolat khamir kontaminan pada yogurt belum pernah dilaporkan sebelumnya. Penelitian dilakukan di Laboratorium Mikrobiologi, Departemen Biologi, FMIPA UI, Depok, dari bulan Desember 2006--Mei 2007. Penelitian bertujuan memperoleh khamir penghasil mikosin asal Kebun Raya Cibodas, yang dapat membunuh khamir kontaminan pada yogurt. Penapisan aktivitas mikosin menggunakan metode gores pada Killer Medium Agar dengan pH 4,4 dan mengandung metilen biru menunjukkan bahwa 17 strain khamir menghasilkan mikosin terhadap 9 isolat khamir kontaminan. Pengujian aktivitas mikosin menggunakan metode sumur menunjukkan bahwa 18 strain khamir penghasil mikosin dapat membunuh 10 isolat khamir kontaminan. Sebanyak 16 strain khamir asal Kebun Raya Cibodas dari kelompok Basidiomycetes memiliki aktivitas mikosin dengan spektrum luas karena dapat membunuh khamir kontaminan dari kelompok Ascomycetes. Sebanyak 2 strain khamir asal Kebun Raya Cibodas dari kelompok Ascomycetes memiliki aktivitas mikosin dengan spektrum sempit karena dapat membunuh khamir kontaminan dari kelompok Ascomycetes. Jumlah sel khamir penghasil mikosin yang digunakan sebanyak 1,38 x 108 sel/ml dan khamir kontaminan sebanyak 3,45 x 107 sel/ml. Khamir mikosinogenik Rhodotorula sp. F. C. Harrison UICC Y-318 dan Rhodotorula sp. UICC Y-325 paling banyak membunuh khamir kontaminan pada yogurt (9 isolat)."