Published on October 17, 2017
1. Disease causing nematodes and its effect on plants Karthick.s 1 st M.Sc., CAS in botany Madras University Guindy campus Chennai
2. CONTENT Objective Introduction What is nematode? Is it harmful to plant? What are all nematode diseases ? What is Rhadopholus similus ? Morphology Lifecycle Symptoms Control measures
3. OBJECTIVE • To learn about nematodes • To learn its characters, role on plants • Understand disease causing nematodes and its affect on plants.
4. Introduction • Nematoda = nematos, meaning thread, eidos, meaning form/like • The Phylum Nematoda consists of the species commonly known as roundworms. • There are approximately 12,000 described species, but the actual number could be many times higher.
5. What are they?
6. Nematodes vs Annelids Both are invertebrates with elongated bodies. Nematodes • Round worm. • Largest 5 cm(small). • Tapered at both ends. • Majority is parasitic. • Pseudocoelom Annelids • Segmented worms • Macroscopic. • Without tapered at end. • Not harmful. • True coelom.
7. What is nematode?
8. Nematodes • are "roundworms“& microscopic in size,
9. • are triploblastic (they have an ectoderm, mesoderm and endoderm).
10. Pseudo – false, coelom - cavity • have a pseudocoelom (a closed fluid- containing cavity that acts as a hydrostatic skeleton to maintain body shape, circulate nutrients, and hold the major organs).
11. • have a thick cuticle covering their body to protect them from digestion.
12. Is it harmful to plant? yes it punctures the cell wall inject saliva(contains enzyme) & take all nutrition. move within body tissues . No it is an important nutrition mineralizer , when nematodes consume bacteria and fungi they release excess ammonium (NH4).
13. What are all nematode diseases?
14. Burrowing disease
15. OVERVIEW Disease : Burrowing disease / Spreading decline Pathogen : Radopholus similis Host : Banana and citrus Part : root /comb
16. What is Radopholus similis ? • Radopholus similis is considered to be the most destructive nematode associated with banana production worldwide. it is a pest of many agricultural crops • It is an especially important pest of bananas and citrus. • More than 50% of nematodes decrease the productive life of banana fields. • known commonly as the burrowing nematode. • It is a migratory endoparasite of roots, causing lesions that form cankers. • Infected plants experience malnutrition.
17. Kingdom : Animalia Phylum : Nematoda Class : Secernentea Subclass : Diplogasteria Order : Tylenchida Family : Pratylenchidae Genus : Radopholus Species : similis
18. Morphology Body - 0.5-0.9 mm in length Lip - rounded in female, knob like in male. Stylet - short and stout in females, slender and rudimentary in males. Oesophagous - forming a lobe , dorsally overlaps to intestine. Vulva - located at middle of the body. Ovaries - didelphic. Tail - blunt end in female and male long tail with bursa.
19. How does it affect the plants? Nematode penetrates root directly Nematode invading root cortex Invaded tissues turn brown Nematodes reproduce and migrate within the root. Invaded cortical tissues collapse and break down Young root may be girdled and their distal portions killed
20. LIFE CYCLE It completes its life cycle within the root cortex, however, juveniles and adults are also present in rhizosphere soil. Optimum reproduction occurs at around 30°C. It does not reproduce below 16-17°C or above 33°C. ranges between 24 and 32°C. it completes its life cycle in 20-25 days,
21. Symptoms • Poor growth • fruit size - Small • Prone to toppling over under high wind pressure . • Purplish streak on the young root. • Reddish brown lesions throughout the cortex
22. Control measures • Azadirachta indica and Allium sativum – apply extract • Paecilomyces lilacinus -(fungus)parasitizes eggs, juveniles and adults of R. similis. It can be applied as dip, soil drench or incorporated into the soil. It is marketed commercially. • Pseudomonas fluorescens -(bacteria) inhibit invasion of R.similis.
23. • Nematicides are generally non-volatile organophosphates or carbamates. Their mode of action is mainly nematostatic, which means they do not kill nematodes, but act on the nematodes’ nervous system and interfere with their ability to hatch from eggs, move, penetrate the roots, feed and reproduce. • Though nematicides are generally effective in controlling nematodes and are easy to use, they are expensive, highly toxic and may have a negative impact on the environment
24. References 1. Cobb, N.A. 1893. Nematodes, mostly Australian and Fijian. F. Cunninghame and Co., Sydney, Australia. 84p. 2. Wehunt, E.J. and Edwards, D.I. 1968. Radopholus similis and other nematode species on bananas. p1-19. In: Smart, G.C. and Perry, V.G. (eds.). Tropical Nematology. University of Florida Press, Gainesville, U.S.A. 3. Stover, R.H. 1972. Banana, plantain and abaca diseases. Commonwealth Mycological Institute, United Kingdom. 316p. 4.The royal horticultural society PESTS & DISEASES. 5.http://www.musarama.org/upload/high/toppled-plant.jpg
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