CP 102 Principles of Plant Disease Diagnosis and Management (PDF)

17/09/2024 CP 102 Principles of Plant Disease Diagnosis and Management What are the characteristics of fungi/ phytopathogeni...

17/09/2024 CP 102 Principles of Plant Disease Diagnosis and Management What are the characteristics of fungi/ phytopathogenic fungi? 1st Semester 2024-2025 Joanne A. Langres, MSc Faculty, DPSS, CSU-CAA 1 2 Plant Pathogenic Fungi Learning objectives ▪ Achlorophyllous - not having chlorophyll and, hence, unable to At the end of the chapter, the student must be able to: engage in photosynthesis. 1. Identify plant diseases caused by plant pathogenic ▪ Eukaryotic - are organisms whose fungi. cells have a nucleus; nuclear 2. Know the different methods of diagnosing diseases membrane that surrounds the nucleus caused by fungi. 3. Perform the fungi isolation. 3 4 3 4 https://www.sciencefacts.net/prokaryotes-vs-eukaryotes.html https://www.sciencefacts.net/prokaryotes-vs-eukaryotes.html 5 6 1  17/09/2024 Plant Pathogenic Fungi Plant Pathogenic Fungi ▪ Heterotroph - obtain food from ▪ They are generally organic matter (living or non-living) filamentous, ▪ Reproduce mainly by spores branched organisms (sexual/asexual) that normally reproduce by spores ▪ Nutrition is by absorption and have walls made ▪ spore-forming microorganism with of chitin and other branched filamentous vegetative polymers structures, true nuclei and cell walls. 7 8 7 8 Plant Pathogenic Fungi ▪ Cell wall is typically present, usually based on glucans and chitin (Eumycota), rarely on glucans and cellulose (Oomycota/ Stramenopila). Source: Vanessa Gelorini https://byjus.com/biology/fungal-cell-wall/ 10 9 10 Plant Pathogenic Fungi ▪ Fungi are eukaryotic, uni- or multinucleate, the thallus being homo- or heterokaryotic, haploid, dikaryotic or diploid ▪ Vegetative thallus is typically a filamentous nonmotile mycelium or hyphae which may be ceonocytic or septated. 11 11 12 2  17/09/2024 Fruiting Structure/ Bodies Plant Pathogenic Fungi - contains the spores ▪ Spore forming, either or both sexual and A. ascocarp (under Phylum Ascomycota) asexual that are typically microscopic ▪ also called ascoma, plural produced in high numbers ascomata, fruiting structure of ▪ Motile spores are confined to certain fungi of the phylum groups (eg. Oomycota) Ascomycota (kingdom Fungi). It ▪ Some produce microscopic or arises from vegetative macroscopic sporocarps (eg. filaments (hyphae) after sexual cleistotehcium, pycnidium, ascocarp, reproduction has been initiated ascocarp basidiocarp) showing characteristic shapes 13 14 13 14 Type of ascocarp Type of Ascocarp 1. Clestothecium ▪ a closed spore-bearing structure in some ascomycetous fungi from which the asci and spores are released only by decay or disintegration. ▪ These typically have bag-like asci cleistothecium 16 15 16 Type of Ascocarp Type of Ascocarp 2. Perithecium 3. Apothecium ▪ A flask-shaped fruiting ▪ cup-shaped with structures, often microscopic the hymenium Microstoma floccosum and/or embedded within either fully exposed the substrate it is fruiting in or (lining the interior a fungal structure called a of the cup), stroma. though this can be inverted and take on strange shapes Urnula padeniana Ascobolus furfuraceus 17 18 17 18 3  17/09/2024 Pycnidium (under Phylum Ascomycota Basidiocarp (under Phylum Basidiomycota) and Deuteromycota) ▪ a flask-shaped fruiting body ▪ also called basidioma, in fungi, a bearing conidiophores and large sporophore, or fruiting conidia on the interior and body, in which sexually occurring in various imperfect produced spores are formed on fungi and ascomycetes the surface of club-shaped structures (basidia). pycnidium Basidiocarp 19 20 19 20 Fungal Habitat ▪ Ubiquitous in terrestrial and freshwater habitats, less Common Symptoms by so in the marine environment. Fungal Disease Fungal Ecology ▪ Fungi can cause general or localized signs and/or ▪ Important ecological roles as saprotrophs, symptoms. mutualistic symbionts, parasites, or hyperparasites ▪ In the majority of cases, fungal infections cause general necrosis of host tissue and often cause Distribution stunting, distortions and abnormal changes in plant ▪ Cosmopolitan/ diverse tissue and organs. 21 22 21 22 ▪ The most distinctive and easily identifiable Common symptoms are: characteristics of fungal infections are the physical presence of signs of the pathogen. ▪ Leaf Spots ▪ Signs include hyphae, mycelia, fruiting bodies and are very common in both biotic and spores of the fungal pathogen are significant clues to abiotic plant disorders. Fungal leaf proper identification and diagnosis of a disease. spots often take the form of ▪ The fruiting bodies of fungi range from microscopic localized lesions consisting of to macroscopic necrotic and collapsed tissue. Leaf spots can vary in size and are generally round and concentric, but can be ovoid or elongated on both 23 leaves and stems of the host 24 23 24 4  17/09/2024 Common symptoms are: Common symptoms are: ▪ Leaf Spots ▪ Anthracnose The typical fungal leaf spot will have a “bulls-eye-like” an ulcer-like lesion that can be appearance consisting of roughly concentric rings that necrotic and sunken. These lesions may display zones of different colors such as yellow, can appear on the fruit, flowers red or purple, and will often have a tan center. As the and stems of the host. spots develop, they are not restricted by the leaf veins as can be the case in bacterial leaf spots. Fungal leaf spots will usually have a dry texture but are not dry and papery. 25 26 25 26 Common symptoms are: Common symptoms are: ▪ Canker ▪ Damping-off a localized necrotic lesion on a rapid collapse and death of very woody tissue, often sunken. young seedling. Either the seed rots before emergence or the seedling rots at the soil line and falls over and dies. Several soil- born fungi cause this disease. The most common genera involved are Fusarium, Rhizoctonia and Pythium. 27 28 27 28 Common symptoms are: Common symptoms are: ▪ Scab ▪ Blight localized lesion on host fruit leaves rapid generalized browning and tubers and other plant parts. These death of leaves, floral organs, infections usually result in a stems and branches. Blights can roughened, crust-like area on the refer to both biotic and abiotic surface of the host disorder Early Blight Symptoms on Tomato Foliage Powdery Scab 29 30 29 30 5  17/09/2024 Common symptoms are: Common symptoms are: ▪ Die-back ▪ Galls progressive death of shoots and enlarged parts of plant organs, twigs generally starting at the tip usually caused by excessive of the infected plant part multiplication or enlargement of plant cells (Clubroot of Crucifers- Plasmodiophora brassicae). 31 32 31 32 Common symptoms are: Common symptoms are: ▪ Mildew ▪ Rust mycelium, fruiting bodies infected plants will most of the and necrotic tissue. time have many small lesions on stems or leaves, usually a rust color but can also be black or white 33 34 33 34 Common symptoms are: ▪ Smut mycelium or black spores on seeds, in the form of galls or seeds “replaced” by spores 35 35 6