Downy Mildew of Maize

symptoms,pathogen and management

1. COLLEGE OF AGRICULTURAL TECHNOLOGY (Affiliated to Tamil Nadu Agricultural University, Coimbatore-3) Kullapuram (Po), ViaVaigai Dam, Theni-625 562 Downy mildew of maize Student Course teacher S.JAMUNA Dr. S. Parthasarathy 2016021014 Assistant Professor (Plant Pathology)

2. Number of fungi downy mildews are Peronosclerospora philippinensis, Peronosclerospora maydis, Peronosclerospora sorgi

3. Peronosclerospora sacchari, Sclerophthora rayssiae var. zeae, Peronosclerospora heteropogon ,

4. Peronosclerospora heteropogan is reported from Rajastan. Dangerous species are P.philippinensis , P.sacchari, S .rayssiae var. zeae P.sorghi

5. It is mostly occurred in South Asian, South East Asian and Pacific region. In India, the disease is more in Tarai regions of Himalayas.

6. ECONOMIC LOSS Yield loss is caused upto 63% due to this disease. In the states of Karnataka,Tamilnadu,Andhra Pradesh causing yield losses of 30% and higher.

7. GLOBAL DISTRIBUTION World: P.sorghi exists in Africa, the Indian sub-continent. South-East Asia and North,Central and South America.

8. INDIA: Andhra Pradesh, Delhi, Haryana, Karnataka, Kerala, Madhya Pradesh, Maharastra , Rajasthan,Tamilnadu .

9. SYMPTOM It appear on leaves as long, broad, yellow, brown and chlorotic stripes. Under surface of the leaf shows wooly white growth of the mycelium. Internodes get shortened and plant becomes stunted.

10. Tassels are malformed. Cob may not be formed, if formed they are without grains. The infected plants may often die. The plants are systematically infected in case of Philippines downy mildew.

11. Brown stripe downy mildew caused by S.rayssiae var. zeae

12. Downy mildew caused by P.philippinensis

13. Downy mildew of maize caused by P.sacchari , the continuous yellowish stripes.

14. Systematic position Domain Eukaryota Superphylum Heterokonta Phylum Oomycota Order Sclerosporales Family Sclerosporaceae Genus Peronosclerospora Species P. sorghi Authority (W. Weston & Uppal ) C.G.Shaw ,(1978)

15. PATHOGEN CHARACTER Conidiophores of P. sacchari emerge through stomata singly or in groups of 2, rarely 3. They are massive and wedge shaped, short, stout stuctures widening gradually towards the upper portion.

16. The conidia are thin walled, hyaline, elliptial , cylindrical or ovate oblong with rounded apex. Oogonia are reddish brown, irregularly elliptical. Oospores on maize leaves are typically round, thin walled.

17. Conidia and Oospores germinate by germ tube. The germ tubes are hyaline and slender, aseptate . They develop from one or both ends of the conidium or from its lateral side .

18. P.philippinensis and P.sachhari are morphologically identical but differ from each other in that the former does not produce Oospores. Conidia of this species are mostly barrel shapped but variable on different hosts.

19. Sporangiophores of S. rayssiae var. zeae are quite distinct from Conidiophores of the above species. They are determinate, unbranched and short. They arise from hypae congregated in the substomatal space.

20. They produce Sporangia sympodially in groups of 2-6. These Sporangia are hyaline, ovate, elliptical, smooth. Germination is by production of 4-8 Zoospores.

21. PATHOGEN OF P.philippinensis

22. EPIDEOMOLOGY Mode of survive: The pathogen mostly survives as oospores present on/in maize seeds or crop depris . The fungus may also survive in many host like S.spontaneum ( Kans grass), S.bicolor , S.halepense and Digitaria sanguinalis .

23. Mode of spread : The pathogen spread through seeds. Seed-borne presence of P.phillipinensis was mentioned in DM of maize while mycelium is present in all parts of the seeds,70% embryos contained oospores and 80% in P.sorghi.

24. FAVOURABLE CONDITIONS The optimum temperature for the production and germination of conidia/sporangia is about 25°C and free water on leaf surface is essential for formation and germination of conidia/sporangia.

25. LIFE CYCLE

26. MANAGEMENT Resistant maize cultivars, Hybrids- Ganga5,Ganga9, Composites, Kisan , Tarun , Naveen, Sweta , Kanchan . Plant maize at least a fortnight before the onset of rains. Incidence of the disease becomes less if planting is done during dry season.

27. Select well drained fields for maize planting or arrange proper drainage to drain out the excess rain water. The disease can be minimized by spraying the foliage with fungicides such as metalaxyl or mancozeb ( 0.3%).

28. Burn the crop residue after the harvest. Practice three year crop rotation to minimize the initial inoculum load in the field.

29. REFERENCE Singh,R.S.,2018.PLANT DISEASES.Tenth Edition.Scientific International ( Pvt )Ltd. New Delhi. Sushil Kumar Singh.,Dinesh Kumar and Adesh Kumar.2015.PLANT DISAESES AND THEIR MANAGEMENT.Kalyani Publisher. New Delhi.

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