Bài giảng Tuyến trùng bướu rễ và cysts

Nội dung text: Bài giảng Tuyến trùng bướu rễ và cysts

1. Bài 9: Tuyến trùng bướu rễ và cysts
2. Meloidogyne • Vào cuối 2004, 106 loài đã được mô tả • Phân bố rấr rộng • Nội ký sinh bắt buộc trong rễ
3. Đặc điểm chung • Gây hại quan trong nhất trong các nhóm TT • Một số loài ký sinh trên 2,000 loại thực vật • Tạo "Đại bào" trong rễ • Tạo bướu trên rễ • Sinh sản đơn tính (parthenogenesis?) • Trứng được đẻ ra ngoài cơ thể, trong một túi nhờn (gelatinous matrix sac)(có thể nhìn thấy trên bề mặt rễ) 500 - 1000 w/con
4. • Root-Knot Nematode was first discovered on peaches in the U.S. in 1889.
5. • Root-knot nematodes are sedentary endoparasites in that the female no longer is motile once she has established a feeding site in the root • The female deposits single-celled eggs in a gelatinous mass at or near the root surface. • Embryonation of the egg begins immediately and continues until a worm-shaped larvae hatches. • This larvae is about 1/60 of an inch long and is in the second stage, having passed through one molt within the egg. • It then migrates either into the soil or to a different location in the root.
6. • The cycle is completed when the female begins laying eggs. Her egg masses normally contain 300 to 500 eggs but may range from almost none under unfavorable conditions to as many as 2,000 under highly favorable conditions.
7. • The larva in the soil penetrates a suitable root by repeatedly thrusting its feeding structure, the stylet, into cells at the surface. After forcing its way into the root, the larva moves between and through cells to the still-undifferentiated conductive tissues. • Within two or three days, the larva becomes settled, with its head embedded in the developing vascula cylinder, and begins feeding. • The nematode then begins to grow in diameter, loses its ability to move, and matures.
8. Meloidogyne
9. Giant cells • As the name implies, giant-cells can grow very large in size. • Triggered by nematode esophageal gland cell secretions, an increase in the production of plant growth regulators has been demonstrated to play a role in this increase in cell size and division. • Root cells neighboring the giant-cells also enlarge and divide rapidly, presumably as a result of plant growth regulator diffusion, resulting in gall formation.
10. At the establishment of a feeding site several dramatic physiological changes occur in both the host plant and the developing nematode
11. • The root-knot nematode feeding site is actually a group of cells known as "giant-cells". • When a nematode initially penetrates a plant cell with its stylet, it injects secretory proteins that stimulate changes within the parasitized cells. • Parasitized cells rapidly become multinucleate (contain many nuclei) as nuclear division occurs in the absence of cell wall formation. • This process is considered to be "uncoupled" from cell division.
12. • Cells never actually divide into new cells; they just get bigger and contain more nuclear material. • This allows the giant-cell to produce large amounts of proteins which the nematode will then ingest. • Giant-cells also act as nutrient sinks, funneling plant nutrients to the feeding nematode • The root-knot nematode does not feed from the cells directly. • It forms a feeding tube (from the esophageal gland cell secretions), secreted from the stylet into the plant cell cytoplasm, which acts as a sieve to filter the cytosol that the nematode ingests.
13. • The nematode feeds upon the giant cells throughout the rest of its life. • Continued enlargement of these cells, rapid multiplication of other cells, and growth of the nematode contribute to the developing root gall, which protects the maturing nematode from the outside environment. The conductive tissues no longer function properly. • Translocation of water and nutrients is impeded and, as a result, top growth is affected adversely. • The heavier the infection burden, the more stunting and chlorosis occur aboveground.
14. M. incognita
15. Phương pháp định danh • Now host range test (J.N. Sasser), • chromosome counts (Triantaphyllou), juvenile head structure (Eisenback), • protein (gel electrophoresis patterns - Esbenshade) • and DNA patterns are used to separate species. • Many of these approaches came out of International Meloidogyne Project.
16. North Carolina (Sasser) Differential Hosts Test for four common species of Meloidogyne Meloidogyn Cotton Pepper Watermelon Tobacco Peanut Tomato e species (Deltapine (California (Charleston (NC 95) (Florunner) (Rutgers) and races 61) Wonder) Gray) M. incognita Race 1 - - + + - + Race 2 - + + + - + Race 3 + - + + - + Race 4 + + + + - + M. arenaria Race 1 - + + + + + Race 2 - + - + - + M. javanica + + - + - + M. hapla - + + - + +
17. Meloidogyne incognita
18. M. javanica
19. Meloidogyne • M. incognita • M. arenaria
20. M. arenaria
21. M. exigua
22. Random amplified polymorphic DNA (RAPD-PCR).
23. DISEASE COMPLEXES • Root-knot nematodes often interact with other soil-inhabiting plant pathogens to form disease complexes • in which the resulting disease is much more severe than components of the complex would cause alone.
24. • Meloidogyne species are known to interact with both Verticillium and Fusarium fungi, which cause wilt diseases of pepper, tomatoes, potatoes, and other plants. In certain situations, the nematode has been • responsible for breaking disease resistance to Fusarium wilt. • Disease complexes often kill plants,particularly when young, whereas the nematodes alone seldom cause such a severe reaction.
25. QuickTime™ et un décompresseur sont requis pour visionner cette image. Developping plants resistant to Root-knot nematodes Meloidogyne spp. Feeding structure = giant cells N Essential for nematode development Microtubule-Associated Protein MAP65-3 Is required to promote disease development and Induced early in giant cells map65-3 KO mutants: defective in giant cell formation nematode death Caillaud et al 2008 IBSV
26. Heterodera schachtii • Life Cycle: A few eggs are deposited externally in a gelatinous matrix, but most are retained in the female body.
27. Heterodera schachtii • When the female dies, the cuticle becomes a tanned, brown, tough protective envelope, the cyst, containing the eggs. • The cysts become detached from the host root and remain in the soil, the contained eggs (often numbering 500 to 600) remaining viable for at least 6 years (Thorne, 1923).
28. Heterodera schachtii
29. Heterodera
30. Heterodera schachtii • Optimum temperature for hatching is 25 C, and for subsequent movement in the soil, 15 C. • Optimum soil moisture is intermediate between saturated and dry (Wallace, 1963).
31. Heterodera schachtii • In the cysts, the eggs become embryonated at the first stage juveniles molt to the second, infective stage. • These individuals may remain dormant in the eggs for several years, but some hatch every year and emerge from the cysts into the soil.