PLP 150C1 1st Edition Lecture 5Outline of Last Lecture I. What is plant pathology?II. Plant diseasesA. Irish Potato FamineB. Bengal FamineOutline of Current Lecture I. Diseases caused by basidiomycetesA. ArmillariaB. Rusts & SmutII. Diseases caused by ascomycetesA. Powdery MildewsB. CankersC. ErgotD. Brown RotE. FusariumCurrent LectureDiseases caused by basidiomycetes• Rusts, smuts, wood decayRhizoctonia Diseases• Sterile mycelium (no spores) and propagate by sclerotia.• Damping off, stem cankers, root rots, web blights of turf. Damping off of cotton is important inarizona, called soreshin of cotton. • Copper and sulfur are good fungicides.Armillaria root rot• produces a large basidiocarp• Soil inhabitant• Destroys wood• Suggested that old stumps be removed & wood from pruning waste not be buried on site.◦ Can kill individual trees, or survive in stumps of infected treed & spread to all trees, can produce millions of spores & can cover thousands of acres. Rusts - perhaps most important basidiomycete disease• Characterized by rust-colored pustules filled with spores• Obligate biotrophs• Many are heteroecious (needs two different hosts to complete life cycle). Very complex biology.• Stem Rust of Wheat - worldwide.◦ Macrocyclic.***Rusts have two different hosts & produces both sexual and asexual spores.◦ Signs and symptoms on Barberry: A lesion, a canker, swelling, etc.Smuts• Attack ovaries of grains & reduces their quality.• Two types of spores, teliospores & basidiospores• Mycelium infects plant tissue & replaces it with fungal tissue• Mycelium cells transform into teliospores.• Signs & symptoms - actual fungal structures, corn appears weak and infected.Mushrooms can cause wood decay!Diseases caused by Ascomycetes• Fruit rots, leaf curl, powdery mildews, leaf spots and blights.• 80% of plant diseases are caused by fungi, and 80% of these fungi are ascomycetes.• Many Cercospora are host specific.Powdery Mildews• Sexual (teleomorph) and asexual spores (anamorph)• Host specific (all biotrophs are)Nectria Canker• Fruit disease• Sexual structure...ascomycetes.• To control the huge wood decay it can cause, chop it down, let it regrow. Remove the infectedtissue out of the orchard. And use dormant spray after it is cut down, so new infections dont’ start.Ergot• Most common on rye and pearl millet• Grain susceptible only when flowering• Sclerotia (mass of hyphae so compacted) mature as seed in grain head matures, and may contain many toxic alkaloids including LSD.• Rye is susceptible when deficient of copper.Brown Rot of Stone Fruit• Fungus can overwinter on twigs or buds or in old fruit called mummies. • Perhaps most important disease of stone fruitFusarium Wilt of tomato• Infects plant through root, and then moves to vascular system, to the blood of the plant. Grows in that conductive tissue and plugs it. Develops so much fungal tissue inside plant that the plant collapses because it can’t find water.• Symptoms and signs: