Biological control agents using antagonistic fungi have the ability to inhibit the development of disease-causing pathogens by various mechanisms such as competition for space and nutrients, antibiosis by producing antibiotics in the form of chemical compounds, and parasitism by entangling pathogenic hyphae. Antibiotic mechanism is a condition in which an organism secretes one or more metabolites that have a negative effect on other organisms. One of the fungi that has the ability as an antibiosis is Trichoderma viride, where this fungus secretes secondary metabolites in the form of a viridiol phytotoxin compound. This study conducted to determine the antagonist mechanism of the fungus T. viride in suppressing the growth of Alternaria solani, Fusarium oxysporum, Rhizoctonia solani, and Sclerotium rolfsii which causes disease in some cultivated plants, as well as what compounds T. viride possesses in suppressing the growth of other pathogens. This research was carried out at the Plant Disease Laboratory, Department of Plant Pest and Disease, Faculty of Agriculture, Brawijaya University from November 2020 to August 2021. The research was conducted using Trichoderma viride as antagonist fungus and Alternaria solani, Fusarium oxysporum, Rhizoctonia solani, and Sclerotium rolfsii as pathogenic fungi. This research consisted of 3 stages, the first stage was rejuvenation and macroscopic and microscopic characterization of pathogenic fungi and antagonist fungi. The second stage is the in vitro antagonist test using the dual culture method using a completely randomized design with 6 replications. The third stage is the phytochemical test of secondary metabolites using 5 test, namely terpenoid and steroid test, the alkaloid test, the flavonoids test, the tannin test, and the saponin test. The results showed that T. viride had an inhibitory ability >50% against four types of pathogens. The mechanism of T. viride antagonist against four treatments, three treatments belonged to the competition mechanism and one treatment belonged to the microparasite mechanism. The content of secondary metabolites of T. viride are steroids and alkaloids.

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Saccharomyces cerevisiae is a common yeast used as a fermenter in the home industry. This yeast is able to grow in media like waste materials. One of the waste materials that can be used as a medium of yeast growth is waste of coconut water. The use of coconut water as a medium of yeast propagation has been widely used in some types of yeasts. The intake of nutrients such as phosphate will make the yeast cells begin to grow and work faster. The yeast cell takes phosphate as ATP. Khamir will turn it into a phosphate polymerization form that is often found within the mitochondria of these cells. S. cerevisiae has the ability not only in terms of fermentation but also can perform other functions in the biological control process. The main methods of this study include the growth test of S. cerevisiae with the addition of a phosphate (KH2PO4), S. cerevisiae growth test by aerator method, yeast antagonist test. The results showed that S. cerevisiae was able to grow higher with the addition of phosphate nutrients (0.5% KH2PO4). This yeast has the potential to control Fusarium sp. The percentage of inhibition was isolate A0 (9,67%), A1 (11%), A2 (10,67%), A3 (12%), A4 (13%), and A5 (6%). Keywords: Yeast, phosphate nutrient, biological control, Fusarium sp.

Anthracnose caused by Colletotrichum musae is one of several important diseases in banana fruit. An effective, cheap, and safe control method is necessary as a postharvest disease control alternative. This research aimed to obtain and identify wild yeast from banana which was isolated from its peel that had antagonist ability effectively in controlling anthracnose disease of banana fruit. This research was started with isolation of C. musae and yeast from banana, followed by in vivo assay with count percentage antagonist level, slide culture, and in vivo assay to know pathogen incubation stage and incident disease level. The yeast that isolated from Ambon variety was Candida sp., Pichia sp., and Metchnikowia sp. from Kepok variety respectively.

Sand is one of the planting media, but the use of sand as a planting medium is still rare due to the low nutrient content. Quartz sand needs the addition of compost to support plant growth. Mycorrhiza can also be added to the growing media. Mycorrhiza is a soil fungus that can symbiosis with the host plant's roots and has a broad influence on pathogenic microorganisms. Mycorrhiza can also increase secondary metabolites in plants. The compound which is the initial signal for plants to form secondary metabolites is salicylic acid. This research aimed to investigate effect mycorrhiza increase plant growth, the content of salicylic acid and reduce the attack of F. oxysporum fungi that cause Fusarium wilt in tobacco plants. This experiment used a completely randomized design with mycorrhiza dose treatment consisting of 6 treatments that are Control (Soil), M0 (AMB-P0K + 0 g polybag-1) M1 (AMB-P0K + 10 g polybag-1), M2 (AMB-P0K + 20 g polybag-1), M3 (AMB-P0K + 30 g polybag-1), M4 (AMB-P0K + 40 g polybag-1) with each treatment consisting of 5 replications. The results showed that AMB-P0K + mycorrhiza was significant at plant height, number of leaves, leaf area, disease index, pathogen incubation and SA contain.