Pythium
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Pythium is a genus of aquatic or soil-dwelling fungi that can cause diseases in plants. It has 92 known species with a cosmopolitan distribution. Pythium infects plant parts above and below ground, causing diseases like damping off, soft rot, and root rot. It has branching filamentous hyphae and reproduces asexually through zoospores, conidia, and aplanospores or sexually through oogonia and antheridia. Infection leads to pale, shriveled seedlings and brown lesions on roots. Control methods include soil treatments, adequate spacing, and lowering humidity to prevent excessive moisture that allows Pythium growth.
Pythium
- 1. Pythium: Introduction, Structure and Reproduction Presented by Dr. E.Gayathiri Department of Plant Biology and Plant Biotechnology Guru Nanak College
- 2. LEARNING OBJECTIVES • HABITAT • SYMPTOMS OF PYTHIUM • STRUCTURE OF PYTHIUM • REPRODUCTION
- 3. Systematic position • Phylum – Heterokonta • Class - Peronosporomycetes • Order - Pythiales • Family - Pythiaceae • Genus- Pythium
- 4. HABITAT • 92 species (28 species from India) • Cosmopolitan in distribution. • Aquatic, terrestrial or amphibious. • They are facultative parasite, saprophytic and parasitic
- 5. Pythium are divided in two types On basis of diseases that affect plant parts In contact above the ground parts In contact with the soil Common disease caused by Pythium Damping off Soft rot Wheat rot or foot rot
- 6. Disease stages Post- Emergence damping-off Pre-Emergence damping-off Source: Pythium Stock Photos & Pythium Stock Images – Alamy alamy.com
- 7. Symptoms of Pythium seedling • Seedlings become pale green • Show a weak , shriveled place of girdle of brown color on the stem near the surface of the soil. Root • lack of small feeder roots • brown lesions in the roots • loss of cortex Stem • Cortical cells are killed (tissue weak) • The infected tissues appear soft and water soaked Soybean seed and seedling diseases ... extension.umn.edu Damping-off: Identifying and Controlling Pathogens in Transplant ...
- 8. Mycelium appears as White, fluffy mass Mycelium branched, inter- or intracellular, multinucleate Filament, Coenocytic Haustoria are not produced Structure of Pythium
- 9. Cell wall is composed of glucan and cellulose Cell wall encloses vacuolated cytoplasm with cell organelles Glycogen is the reserve food mater. Structure of Pythium
- 13. • Oogonia and antheridia are produced • They are very close to each other. • They are often present on the same hypha. • Antheridium is present just below the oogonium Sexual Reproduction - Oogamous type
- 14. Fertilization tube is formed, the male nucleus from antheridium passes through this fertilization tube and enters the oosphere. Two nuclei fuse to form zygotic nucleus. Oogonium is globose. It contains a single oosphere. surrounded by periplasm. Young oosphere is multinucleate. But later on it becomes uninucleate. Antheridium is club shaped and multinucleate in the beginning. But later on it becomes uninucleate. Fertilized egg secretes a thick wall and changes into an oospore
- 16. High temperature favours mycelium formation. But low temperature favours the production of zoospores. Mycelium are produced directly, or it may produce a short hypha. This hypha develops a sporangium at its tip. Reduction division takes place bcfore the germination of oospore Oospore germinates after a period of rest Germination
- 18. LIFE CYCLE OF PYTHIUM
- 19. Control of the Disease Caused by Pythium The soil treatment of nursery beds by the use of chemicals such as formaldehyde diluted in proportion of one part to 50 parts of water and Bordeaux mixture ( ½ gallon per square foot) To control pre- emergence phase of ‘damping off Blitox-50 and Arasan. Thin sowing to avoid over- crowding Adequate exposure to air and light of the seed beds Prevention of excessively moist conditions Drenching soil with 0.2% Fytolan, 0.5% Perenox and 0.2% Flit 406 Lowering the humidity of the atmosphere