RICE TUNGRO VIRUS

SYMPTOMS,PATHOGEN AND MANAGEMENT

1. COLLEGE OF AGRICULTURAL TECHNOLOGY (Affiliated to Tamil Nadu Agricultural University, Coimbatore-3) Kullapuram (Po), ViaVaigai Dam, Theni-625 562 RICE TUNGRO VIRUS STUDENT: COURSE TEACHER: ATCHAYA. M Dr. S. PARTHASARATHY (2016021005 ) Assistant Professor (Plant Pathology).

2. SIGNIFICANCE Tungro means degenerated growth. Tungro is called as cancer because of severe damage. Tungro was first diagnosed in 1963. The disease is reported from Philippines, Malayasia , Indonesia, Thailand, India and Pakistan.

3. Rice tungro virus disease is one of the most damaging and destructive of rice in south and south east Asia and also in southeren parts of china ( Krishnaveni et al., 2011). Indonesia is perpetually affected by the disease, the area affected varying from 16,000 to 25,000 ha annually. The annual loss due to tungro is estimated at US $ 1.5 billion globally ( Herdt , 1988).

4. DISTRIBUTION IN INDIA West Bengal Andhra Pradesh Madhya Pradesh Bihar Assam Tamil Nadu Karnataka Kerala

5. DISTRIBUTION IN ANDHRA PRADESH The distribution of rice tungro has become sporadic in most of the rice growing tracts of Andhra Pradesh especially in some of the districts like Medak and Nalgonda . Till now the disease has been reported from East Godavari, Chittoor and Prakasam districts of Andhra Pradesh.

6. DISTRIBUTION IN WORLD Africa Asia Australia Europe South America North America

7. GLOBAL DISTRIBUTION OF TUNGRO VIRUS https://www.plantwise.org

8. SYMPTOMS Symptoms depend upon host cultivar, in the cultivar TN 1, seedlings show stunting with mottling and yellowing of leaves. Reduced tillers, yellowing and orange yellow colouration of leaves is a common symptoms. Delayed flowering Most panicles sterile or partially filled grains

9. Yellowing from tip to downwards Stunted with reduced tillering www.Knowledgebank.irri.org>item>tungro

10. Yellowing and orange yellow colouration of leaves Tungro virus affected field www.agritech . tnau.ac.in

11. PATHOGENS Tungro bacilliform virus Tungro spherical virus www.agritech.tnau.ac.in

12. PATHOGENS https://link.springer.com.article

13. PATHOGENS CHARACTERS RTBV – dsDNA bacilliform virus, which cause mild stunting and yellowing of leaves. It belongs to Budna virus group, the particle 100-400 nm long and 30-35nm in diameter. RTSV – ssRNA virus, which causes only very mild stunting, no without leaf symptoms. It is isometric with a diameter of 30-33 nm.

14. SYSTEMATIC CLASSIFICATION Group : Group vii ( dsDNA ) Family: Caulimoviridae Genus : Tungro virus Species: Rice tungro bacilliform virus (Salto in 1975) Group : Group iv ( ssRNA ) Family : Sequiviridae Genus : Waikavirus Species: Rice tungro spherical virus

15. GREEN LEAF HOPPER VECTOR Tungro viruses are transmitted by six leafhoppers species, which are in the genus of Nephotettix s pecies. Nephotettix virescens lays its eggs in batches of up to 44 in the tissues of leaf sheath of rice tillers . After hatching, there are five nymphal stages before adult emergence. At the optimal temperature for development (30 to 35 º C ).

16. VECTORS Nephotettix virescens (Green leaf hopper) Nephotettix nigropictus Nephotettix malayanus Nephotettix parvus Nephotettix apicalis

17. HOSTS Oryza species are the main host but at least 63 species of grasses can be infected . Natural occurrence on grasses in and around rice fields is reported. However, all except Oryza species are poor hosts of the vectors. Horticultural crops - Black pepper, Toro, Cocoa and Yam.

18. DISEASE CYCLE

19. VIRUS-VECTOR INTERACTIONS When young (nymphs) and adult green leafhoppers feed on diseased plants, virus particles get attached to mouth parts( stylets ). As these insects fly and feed on other plants, the virus particles from the stylets get introduced into healthy plants. The insects pick up virus particles within 7 minutes of feeding and can transmit these particles to other healthy plants. Generally, tungro virus disease symptoms appear

20. Transmission mainly by the leaf hopper vector Nephotettix virescens Males, females and nymphs of the insect can transmit the disease. Both the particles are transmitted semi-persistently, in the vector the particles are noncirculative and nonpropagative . Plants infected with RTSV alone may be symptomless or exhibit only mild stunting.

21. RTBV enhances the symptoms caused by RTSV. RTSV can be acquired from the infected plant independently of RTBV, but acquisition of RTBV is dependent on RTSV which acts as a helper virus. Both the viruses thrive in rice and several weed hosts which serve as source of inoculum for the next.

22. EPIDEMOLOGY Mode of spread-Vector borne ( Nephotettix virescens ) Primary source for tungro , includes: Stubbles of previous crops Infested plants in nearby rice fields

23. FAVOURABLE CONDITIONS Presence of virus sources Presence of vector Age and susceptibility of host plants All growth stages of the rice plant specifically the vegetative stage. Ecosystem: Irrigated and rainfed lowland ecosystems.

24. DIAGNOSTIC METHODS There are 5 different diagnostic techniques for tungro 1) Symptomatology 2) Transmission test 3) Iodine/starch test 4) Serological test 5) Electron microscopy The application of one technique or a combination of several techniques will greatly help in correct identification.

25. MANAGEMENT OF RICE TUNGRO VIRUS CULTURAL METHODS Planting of resistant varieties against tungro virus disease is the most economical means of managing the disease. Use  Resistant varieties like IR 36,  IR 50, ADT 37,   Ponmani , Co 45, Co 48, Surekha , Vikramarya , Bharani ,   and white ponni .

26. RESISTANT VARIETY

27. CULTURAL METHOD Neem seed cake applied at 5 kg/0.032 ha of nursery followed by foliar spray of 5% neem kernal extract in the main field reduces vector population and incidence of tungro ( Rajappan et al. , 2000).   Plouging and harrowing the field to destroy stubbles right after harvest in order to eradicate other tungro hosts are also advisable. Destruction of weed hosts on bunds.

28. Neem cake Ploughing to incorporate the stubbles www.agritech.tnau.ac.in

29. MECHANICAL METHOD Light traps are to be set up to attract and control the leaf hopper vectors as well as to monitor the population. This should be practiced every day.

30. CHEMICAL METHODS Leaf yellowing can be minimized by spraying 2 % urea mixed with Mancozeb ( Indofil M-45) at 2.5 gm/lit. Instead of urea foliar fertilizer like multi-K (potassium nitrate) can be sprayed at 1 per cent which impart resistance also because of high potassium content. Spray insecticides twice, 15 and 30 days after transplanting .

31. CHEMICAL METHODS Spraying of urea + mancozeb Apply carbofuran

32. BIOLOGICAL METHODS Two fungi, Beauveria bassiana and Paecilomyces amoeneroseus are reported as parasites of rice green leaf hopper, Nephotettix virescens . Spray of conidial suspension of the fungi on rice plants kills the vectors ( Niazi et al., 2002 ).

33. REFERENCES Rangaswami , G and Mahadevan ., A. 1999. Diseases of Crop Plants in India. PHI learning private limited, New Delhi. Singh. R.S., 2009. Plant Diseases. Oxford and IBH Publishing CO. PVT.LTD, New Delhi 110 049.