Fungi as Biological Control Agents - Lecture Notes PDF

Fungi as biological control agents ➢Fungi have been used to control – insect pests ; these are most effective in glasshouses – phytopathogenic fungi ; most effective in soil Fungi to control insect pests ➢>1 billion dollars spent each year in USA to control insect pests ; only 5% of this on BCAs ➢...

Fungi as biological control agents ➢Fungi have been used to control – insect pests ; these are most effective in glasshouses – phytopathogenic fungi ; most effective in soil Fungi to control insect pests ➢>1 billion dollars spent each year in USA to control insect pests ; only 5% of this on BCAs ➢over 400 species of fungi attack insects and mites, ➢Typical infection cycle Fungi to control insect pests (2) Both are Verticillium lecanii kills whitefly and thrips in 10-14 days kills aphids in 7-10 days Verticillium lecanii ➢ produces spores in liquid fermentors ➢ fresh spores are ‘sticky’ so they attach to the insect, which becomes contagious ➢ spores do not need to be ingested ➢ germination needs a rh >95%, at 15 - 18 oC for 12 h. Fungi to control phytopathogenic fungi • Mechanisms of control – Parasitism of the pathogen by the BCA – Production of antibiotics, BCA poisons the pathogen – Competition for nutrients, water, space Parasitism Fungi that parasitize other fungi – ‘mycoparasites’ (many are Zygomycetes which are biotrophic and produce haustoria) Most potential shown by necrotrophic mycoparasites: Pythium oligandrum (oomycete!) Lysis of host hyphal cell Host: Botrytis cinerea Colonisation of host Host: Fusarium culmorum Production of antibiotics Trichoderma spp. produce antibiotics (trichodermin; gliotoxin) “Trianum” (Koppert) sold for control of a range of fungal diseases including B. cinerea infection of grapes. Competition Control of 'butt rot' in conifers Phlebiopsis Heterobasidion x x x Control of 'butt rot' in conifers Aerial view of a young pine plantation in the Thetford region of Norfolk, England. Two large, spreading disease gaps are shown by arrowheads near the top of the image. A view of the forest canopy within a disease gap caused by H. annosum. Several of the trees have died, while others are growing poorly and will not be commercially viable As the trees die, Heterobasidium annosum grows up to the soil surface and produces bracket-shaped fruitbodies just above or within the forest litter layer. The fruiting bodies release basidiospores that can be wind-dispersed and infect freshly exposed stump surfaces to spread the infection. Control of 'butt rot' in conifers (2) Spores of Phlebiopsis gigantea produced in liquid culture Fungi – tools and microbial cell factories in industries, old and new Food and Drink: Yeast • baking and brewing • Saccharomyces cerevisiae C6H12O6 2C2H5OH + 2CO2 • S. cerevisiae – yeast extract paste “Marmite” Food and Drink: Soya bean products Soya beans: positives and negatives Improvement: fermentation of beans with Aspergillus oryzae Production of soy sauce: Food and Drink: Quorn® mycoprotein ➢Quorn®: mycelia of Fusarium graminearum (venenatum) ➢Developed by Rank Hovis MacDougall (1950s) – concerns in protein content of food. ➢1980 - approved for human consumption ➢Demand - high protein; low fat; high fibre ➢Grows on glucose syrup – made from a cheap source of carbohydrate (wheat starch) ➢Ammonia – nitrogen source ➢Filaments can be spun, and flavoured, Muscle fibers to resemble meat Fusarium mycelium 1985: first retail product 1985: first retail product (2) Fungal cell factories Enzymes produced commercially by Aspergillus niger Glucoamylases: liquid starch to high glucose syrup (baking, brewing, mycoprotein) Pectinases: breakdown pectins in plant cell walls (fruit juices) Glucose oxidase: food preservation; diagnostic tests Phytases: improvement of animal feed Cancer from crisps! Daily Mail: September 13, 2008 Fungal cell factories: The Problem: Starch based foods cooked at high temperatures (e.g. Crisps, biscuits, snacks) recently discovered high levels of acrylamide - carcinogen Acrylaway® Novozymes Inc. Acrylaway® Pretzels were produced at Reading Bakery Systems (RBS). Substantial reduction (> 90%) in acrylamide was found for a dosage of 70-145 ppm Acrylaway. Scource: Novozymes Inc. Fungal cell factories: Citric acid produced commercially by Aspergillus niger Excess sugar Limited trace metals (Mn; Fe) Fungal cell factories: drugs Antibiotics: penicillin Penicillium notatum ➢1928: Alexander Fleming ➢Developed by Howard Florey and Ernst Chain (Oxford) ➢1941: first life saved and widely used by end of WWII ➢Improved yields from 2 mg to 30 g l-1 ➢Chemically altered semi-synthetic penicillins (methicillin; ampicillin) Fungal cell factories: drugs (2) Statins ➢High plasma cholesterol levels is an important risk factor in coronary heart disease ➢Most of the body’s cholesterol is synthesised directly from intracellular pre-cursors. ➢Statins are fungal metabolites that inhibit the biosynthesis of cholesterol and are used to reduce plasma cholesterol levels.