Seed Health Management for Better Productivity - Govind Ballabh ...

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(Seed Health Management for Better Productivity)Ustilaginales_______________________________________________________Cup-shapedbasidiocarppresentNo basidiocarp formed_____________________________Promycelium septate, Promycelium septate,basidiospores produced basidiospores formedlaterally from each cell apically in a clusterof the promyceliumUstilaginaceae(Smuts)Tilletiaceae(Bunts)Ustilago sagetum tritici Tilletia foetidaU. hordeiU. avenae T. cariesU. kolleri Neovassia horridaU. scitamineaU. maydis N. indicaTolyposporium penicillariaeSphacelotheca sorghiS. reilianaVarious smut diseases caused on different hosts are described as belowLoose smut of Wheat (Ustilago sagetum tritici)Loose smut occurs more seriously in humid areas than in dry areas. In India, the disease ismore prevalent in northern parts resulting in 3-4 % crop losses however some individual fields mayshow up to 20 % smutted heads. The disease is characterized by the presence of black smutspores in place of grains which later are blown away by wind leaving behind the bare rachis. Asthe pathogen is internally seed borne (embryo infection), seed treatment is the most effectivecontrol measure including hot water treatment, solar treatment and seed dressing with systemicfungicides viz vitavax (2 g/kg), bavistin 2.0-2.5g/kg and raxil 1g/kg. The tolerance levels in thefield for loose smut of wheat are fixed at 0.1 and 0.5 % for foundation and certified seed,respectively. The isolation distance is of 150 m.Flag smut of wheat (Urocystis agropyri)The disease has been appearing and causing significant losses since 1848 in Australiafrom where it is believed to be introduced into India and spread to various wheat growing areas.The disease was observed to be in severe from in 1964-65 in Rajasthan and in 1971 in Kullu (HP).Usually up to 10% loss has been common due to this disease. The leaves of infected plantsbecome twisted and assume a dropping habit, and the plant remains sterile bearing no grains.Grayish black bands running parallel to veins (having smut spores) also appear on older leaves.- 122 -
(Seed Health Management for Better Productivity)The disease perpetuates through seed and soil, so same seed treatment as for loose smut iseffective. To avoid soil inoculum, shallow sowing is recommended. Sowing in acidic or sandy soilsshould be discouraged, as in such soils, the disease incidence is more.Karnal Bunt of Wheat (Neovossia indica)The disease causes 5-20 % losses in some wheat cultivars but annual yield loss of 0.2-0.3% of total production has been reported from Punjab. The disease initially being reported fromIndia (Karnal) has now assumed international significance because of enforcement of quarantineby more than 20 countries. The disease has been reported from J&K, HP, UP, MP, WB, Haryanaand Rajasthan. Though the disease does not cause significant yield losses, it is responsible fordeterioration of quality. Infected seeds also show significant reduction in seed germination andvigor. As the disease is initiated by air borne sporidia at the time of flowering, seed treatment is ofno value and hence different strategies viz. crop rotation late sowing, avoiding use of excessivenitrogen and irrigation, foliar sprays (propiconazole and tebuconazole) have been recommended.The tolerance levels for karnal bunt of wheat are fixed at 0.05 and 0.25 % for foundation andcertified seed, respectively.Hill Bunt of Wheat (Tilletia caries and T. foetida)Hill bunt causes about 10-20 % yield losses, being restricted to northern hilly areas,however sporadic appearance in plains have been reported which might be due to use ofcontaminated seed from hills. The infected ear-heads remain green for a longer period and emit afoul smell due to presence of trimethylamine which is characteristic feature of the disease. Beingseed borne the disease can be effectively controlled by the seed treatment with the samechemicals as used for loose smut of wheat.Covered smut (Ustilago hordei) and loose smut (U. nuda) of BarleyCovered smut of barley is more common than loose smut and has been reported fromnorthern parts of India, causing considerable losses on susceptible varieties. Infection of both thesmuts leads to the production of black mass of smut spores in place of grains. However the sporemass is covered by a persistent membrane (epidermis) in covered smut, the thin membranecovering the spores in loose smut ruptures during emergence, and a bare rachis is left after thedispersal of spores. Mode of infection in case of covered smut is through seedling while loosesmut fungi enter through florets. Loose smut being internally seed borne and covered smut beingexternally seed borne, seed treatment as in case of loose smut of wheat has been the effectiveand economical. Hot water treatment has also been recommended against loose smut of barley.Covered smut (U. kolleri) and loose smut (U. avenae) of OatsOats suffer from both the smuts, which are worldwide in occurrence. Usually, the twodiseases occur simultaneously in the same field. Often the covered smut is more common than the- 123 -
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potential. An improvement in qualit
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9. Session Arrangement CommitteeDr.
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9. Dr. Pradip Kumar BorahSr. Scient
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TRAININGONANNEXURE-IIISEED HEALTH M
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ANNEXURE-IVCENTRE OF ADVANCED STUDI
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SundayApril 6MondayApril 7TuesdayAp
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TuesdayApril 15WednesdayApril 16Thu
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