It is the most important human food grain and ranks second in total production as a cereal crop behind maize and the third being rice.
Wheat is the staple food for over ten billion people in as many as 43 countries of the world.
Wheat provides nourishment to 35% of world population.
Wheat cultivation has traditionally been dominated by the northern region of India. The northern states of Punjab and Haryana Plains in India have been prolific wheat producers.
Today, India is exporting sufficient quantities of all types of wheat and extensive research efforts are underway for improving its cereals and grain output in the years to come.
The major Wheat production State are Uttar Pradesh, Punjab, Haryana, Madhya Pradesh, Rajasthan, Bihar, Maharashtra, Gujarat, Karnataka, West Bengal, Uttaranchal, Himachal Pradesh and Jammu & Kashmir.
The share of wheat in total food grain production is around 35.5 % and share in area is about 21.8 % of the total area and their food grain (Rao, 2006).
Seed enterprises consider ‘wheat seed’ to be of secondary importance, since it is a self-pollinating crop and the grain can be used as seed, farmers tend to replant their own seed. In last ten years significant efforts have been made for commercial exploitation of hybrid wheat through the use of gametocide and CMS lines. Today France and Italy are at the verge of commercial release of such wheat hybrids for grain purposes.
90.0 m tons of wheat to feed Indian population by the year 2030 A.D.
O R I G I N
The exact place and date of the origin of wheat plant that we recognize today is unknown.Hexaploidwheats, widely grown to day thought to have evolved before 7000 BC in an area fromjust south of the Caspian Sea in Northern IranEastward into Northern Afghanistan .
De Candolle believed – Valley of Euphrates and Tigris
Origin of Durum wheat probably Abyssinia
Soft wheat groups – In the region of Western Pakistan, SW Afghanistan, and Some parts of mountainous Babshara
Major cultivated species of wheat
Durum - (T. durum) The only tetraploid form of wheat widely used today, and the second most widely cultivated wheat today.
Einkorn - (T. monococcum) A diploid species with wild and cultivated variants . One of the earliest cultivated, but rarely planted today.
Common Wheat or Bread wheat - (T. aestivum) A hexaploid species that is the most widely cultivated in the world.
Emmer - (T. dicocum) A tetraploid species, cultivated in ancient times but no longer in widespread use.
Spelta - (T. spelta) Another hexaploid species cultivated in limited quantities.
Seed development Stages in Wheat Kernels at various stages during grain filling: a) kernel at watery ripe b) kernel at late milk c) kernel at soft dough d) kernel at hard dough showing loss of green color e) kernel ripe for harvest Physiological maturity: When the kernels have attained maximum dry weight it is physically matured. Note the green color is gone from the peduncle and head parts.
Cultural Practices for Seed production of Wheat
Planning for wheat seed production Land requirement : Land to be used for seed production of wheat should be:
It is sufficient to isolate seed fields with a strip of 3 meters all around which is planted with a non-cereal crop, or left uncroped.
In cases where variety is susceptible to diseases caused by Ustilago spp. ( eg. loose smut) an isolation distance of 180meters between seed field and other fields of wheat is recommended
As per Indian minimum seed certification standards require only 150 m isolation from other wheat fields where in loose smut infection is in excess of 0.1% in the case of foundation seed production and 0.5 % in the case of certified seed production.
Cultural Practices Time of Sowing:
Long duration varieties like C 306 should be sown during the first fortnight of November.
Short and medium duration varieties like Sonalika, HD 1982 should be sown during the second fortnight of November.
The optimum time of sowing for wheat is when the mean daily temperature is 23±3°C and for good tillering temperature should range between 16-20°C.
Preparation of Land
Deep ploughing with a soil turning plough.
Running a harrow before the pre-sowing irrigation.
Give a light shallow ploughing or discing after pre-sowing irrigation.
Levelling is an important part of seed bed preparation.
Broadcast BHC, 10 per cent dust at 25 kg per hectare just before the last harrowing or ploughing. It may be added to the fertilizer and applied.This will prevent white ant and Gujhiaattack.
Source of seed :
Obtain nucleus/breeder's/foudation seed from a source approved by the certification agency.
The recommended seed rate for seed crop is
85-100 kg per ha. The seed should be treated with systemic fungicide to control loose smut. Spacing : The row distance for seed crop should be kept at 22 to 23 cm to facilitate roguing and inspection work. For late sown wheat reduce the line spacing to 15-18 cm Crop Rotation :
Wheat is mainly grown in rotation with rice, sugarcane, arhar (pigeon pea) and sorghum, cotton, pearl millet, cluster bean, sorghum, groundnut,
Method of sowing
The seed crop is sown in rows with seed drill, or behind the plough in furrows.
For control of broad-leaved weeds spray 2-4 D at@ 0.5kg active ingredient per hectare in 750 liters of water after 25 to 30 days of sowing.
For control of Phalaris minor or wild oats make a pre-emergence application of Pendamethalin (stomp) @ 1 kg per ha in 750 liters of water or spray Isproturon @ 1 kg per ha in 750 liters of water after 35 days of sowing.
Roguing Two or three roguings may be necessary
First roguing :
Just ahead of the flowering stage, or during flowering to remove any off-type plants which are obvious at this state of growth.
Second roguing :
Just after flowering is completed, and before the crop starts to turn colour.
should be done after the ear heads turn colour and start to mature.
Masses of black teliospores are produced in narrow strips just beneath the epidermis of leaves, leaf sheaths and occasionally the culms. The epidermis of older diseased plants tends to shred, releasing the teliospores
:generally it is not an economically important disease, but where present, yield losses can range from trace amounts to moderate levels.
Control: Seed treatment with Carboxin (75 WP @ 2.5 gm/kg seed) or Carbendazium (50 WP @ 2.5 gm/kg seed) or Tebuconazole (2DS @ 1.00 gm/kg seed) ,two days before sowing.
The entire inflorescence, except the rachis, is replaced by masses of smut spores. The disease can occur wherever wheat is grown
Yield losses depend on the number of spikes affected by the disease; incidence is usually less than one percent and rarely exceeds thirty percent of the spikes in any given location.
Control: Seed treatment with carboxin (75 WP @ 2.5 gm/kg seed) or carbendazium (50 WP @ 2.5 gm/kg seed) Seed treatment with fungicide should be done one or two days before sowing.
Cover Smut (Tilletia tritici ) Plants may be slightly shorter, and the heads are usually darker green than normal and remain green for a longer period. Bunt infections result in the complete replacement of the seed contents with a mass of smut spores. When crushed, the infected grain releases a fine black-brown powder with an odor like rotten fish. Bunt is potentially the most devastating smut disease. Control:
seed treatment with Foliarflo-C , Maxiflo, Vitaflo C, or Vitavax
Do not sow seed visibly infested with bunt (cover smut)
When bunt balls are crushed, they give off a fetid or fishy odor. Infected spikes tend to be bluish green in color (or darker), and the glumes tend to spread apart slightly; the bunt balls often become visible after the soft dough stage . A slight reduction in plant height is typical of common bunt.
Considerable yield losses can occur when susceptible cultivars are grown or chemical seed treatments are not used.
Initial infection sites tend to be irregular in shape, oval to elongated chlorotic spots or lesions. As these sites expand, the centers of the lesions become pale, straw colored, and slightly necrotic, often with numerous small black dots (pycnidia) .
The lesions of septoriatritici blotch tend to be linear and restricted laterally
Major losses can occur, through seed shrivelling and lower test weights, if these diseases reach severe levels prior to harvest.
Take-all (Gaeumannomycesgraminis f. sp. tritici )
This fungus causes rotting of the roots and lower stems. Basal stem and leaf sheath tissues, as well as roots, may turn a shiny black color.
When infection occurs early in the crop cycle, the number of tillers is often reduced and spikes are often sterile.
Take-all is widespread in monocropped areas and has been known to cause considerable yield losses in winter wheat and fall-sown spring wheat areas, especially where liming or minimum tillage is practiced.
Control: Later plantings are better,Use Ammonium Nitrate,Fertilize early, Use higher rates of fertilizer, Do not lime take-all infested soil, Rotate with other crops, corn may produce scab in wheat
At flowering, infected florets produce a yellowish, sticky, sweet exudate (containing conidia) that is visible on the glumes. As the spike matures, kernels of infected florets are replaced by brown to purplish black fungal structures (sclerotia or "ergot bodies") .
The disease is more prevalent in cool, humid climates.
Yield losses tend to be small, but losses due to discounted grain quality can be significant and occur worldwide
…………………………………………………………………………………………….. Common and Dwarf Bunt (Tilletiacontroversa )
Bunt balls of Dwarf bunt is nearly spherical. When bunt balls are crushed, they give off a fetid or fishy odor. Infected spikes tend to be bluish green in color (or darker), and the glumes tend to spread apart slightly; the bunt balls often become visible after the soft dough stage.
Considerable yield losses can occur when susceptible cultivars are grown or chemical seed treatments are not used.
Stem Rust or Black Rust(Pucciniagraminisf.sp. Tritici)
Pustules (containing masses of urediospores) are dark reddish brown, and may occur on both sides of the leaves, on the stems, and on the spikes .
If infection occurs during the early crop stages, the effects can be severe: reductions in tillering and losses in grain weight and quality. Under favorable conditions, complete crop loss can occur.
Control: Growing , varieties, like GW 322, HD 2781, HUW 510, NIAW 34, MACS 2846(D), Raj 4037, In Peninsular Zone
CZ, PZ & SHZ ………………………………………………………………………………… Powdery mildew on wheat (Erysiphegraminis f. sp. Tritici)
the first visible symptoms of this disease are white to pale gray, fuzzy or powdery colonies of mycelia, and conidia on the upper surfaces of leaves and leaf sheaths (especially on lower leaves),and sometimes on the spikes. Older fungal tissue is yellowish gray.
Powdery mildew can cause major yield losses if infection occurs early in the crop cycle and conditions remain favorable for development so that high infection levels are reached before heading.
Control: one spray of propiconazole (25 EC) @ 0.1 % at earhead emergence or appearance of disease (whichever is earlier) is recommended for the powdery mildew prone areas.
Karnal bunt is not easily detected prior to harvest, since it is usual for only a few kernels per spike to be affected by the disease. Following harvest, diseased kernels can be easily detected by visual inspection: a mass of black teliospores replaces a portion of the endosperm, and the pericarp may be intact or ruptured.
Diseased kernels give off a fetid or fishy odor when crushed.
Karnal bunt is a relatively minor disease. Actual losses in yield are minimal, but the disease is on the quarantine lists of many countries and therefore of importance in world grain trade.
Russian wheat aphids damage small grains by injecting toxic saliva into the leaves and by sucking sap from the leaves. Yield losses of 50 per cent or more have been attributed to Russian wheat aphids.
The feeding of Schizaphisgraminin is especially damaging, resulting in the development of necrotic areas sometimes accompanied by purpling and rolling of the infested leaves. The feeding of Diuraphisnoxis produces long white stripes on the leaves , leaf rolling, postrate growth habit, and sterile heads
Control :. foliar spray of Imidacloprid 200SL @20g a.i./ha on border rows at the start of the aphid colonization be given
Wheat midge Damage : midge is a seed feeder and infests a wheat plant during heading through early flowering Crop injury is caused only by the larval stage. After hatching, wheat midge larvae crawl down to feed on the developing wheat kernel. Control: Early planting is the most useful cultural control method. This method is suitable only for hard red spring wheat. Crop rotation: . Planting crops that are not susceptible to wheat midge, such as soybean, sunflower, flax, pea, lentil, chickpea, oat or corn, will reduce the reproductive opportunities for wheat midge Use of Resistant Varieties: A highly effective resistance trait called Sm1 which reduces survival of early instar wheat midge. Chemical: insecticides are not effective in controlling older wheat midge larvae, which are protected within the glumes as they feed on the developing kernels Organophosphate insecticides with the active ingredient chlorpyrifos can kill eggs.
Grasshopper Insects with hind legs adapted for jumping. They include the longhorned grasshoppers, pygmy grasshoppers, and shorthorned grasshoppers, or locusts. They subsist on vegetation and are distributed worldwide wherever vegetation grows. Grasshoppers are 3 to 13 cm (1 to 5 in) long when fully grown. They develop by gradual metamorphosis: The nymph is initially wingless and gradually comes to resemble the adult as it grows through progressive molts. Only the adults can fly. Control: Deep plough during winter will kill eggs Malathion@4-5kg/ha , Sevin @ 1kg active ingredient /ha Hessian Fly (Mayetiola destructor) Damage : Hard red spring wheat infested in the spring and early summer will take on a dark bluish-green color and become distinctly thickened and stunted. Control: Resistant variety : Guard released by South Dakota in 1983) Crop rotation: oat,corn,sunflower Tillage: Moldboard plowing in the fall after the first killing frost. Chemical: phorate 20% granules for both hard red spring wheat and winter wheat and disulfoton 15% granules for winter wheat only.
Wheat Stem Sawfly Sawfly damage is threefold. First, they cause 10 to 14 percent grain yield reduction by their tunneling activity in the infested stems. Additional loss occurs when sawfly-cut stems fall to the ground and become unharvestable. Control: Resistant varieties: Ernest, Glenman, Leader, Tioga, Fortuna, Lancer CROP ROTATION: non-host crops should be considered in these areas. Tillage: shallow fall tillage will provide up to 90 percent sawfly control CHEMICAL: No effective chemical treatment is available ……………………………………………………………………………………………………. True Army worm Can be serious pest of wheat when populations reach large numbers. They sometimes start at one portion of the field and devour everything in their path.
Treat wheat plant if 6-8 larvae per square foot are present and wheat is still in the milk stage. Once past the milk stage, it can tolerate higher populations and treatment is not usually recommended unless larvae are cutting wheat heads.
Control :carbaryl (Sevin XLR Plus 4)@32 - 48 oz/ac, methyl parathion 4 (Methyl 4)@24oz/ac, spinosad (Tracer 4)@1.5-3oz/ac.
Insect Pest Control Measures Adopt recommended IPM methods
Determination of physiological maturity in dicoccum wheat(Upparet al., 1999)
field experiments were conducted at the mainresearch station , UAS, dharwad during rabi 1997- 98 & 1998- 99 to determine the physiological maturity for getting high quality seed in dicoccum wheat varieties .
The results indicated that the dicoccum wheat varieties DDK-1001, DDK-1009, DDK-1013 and NP-200 attained physiological maturity at 35 DAA, 35DAA, 40DAA, 45DAA, respectively and at this stage, the seeds had higher dry matter accumulation with maximum germination, root length, shoot length and vigour indices.
Harvesting and Threshing
Soon after maturity, the seed crop should be harvested to avoid shattering and losses due to uncertain weather.
Most suitable stage is grain moisture of 20-25%.
Mechanical harvesting is a common practice for seed production fields.
Breeder and pre-basic seed are harvested by plot combine and do not constitute many problems.
foundation and certified seeds have to be harvested with commercial combine harvesters.
The most critical factors to be considered are :
i)seed moisture content , ii)mechanical damage iii) cleanliness of equipment.
For seed crops, dry weather during ripening and harvesting is essential.
Threshing or combine harvesting at 16 to 19 percent moisture content reduces mechanical damage (Thompson, 1979).
Harvesting may be done by sickle , Combine or reaper, and later the threshing with stationary thresher.
Threshing equipment should be cleaned after threshing other wheat varieties.
The threshing floor must be thoroughly cleaned to prevent mixtures.
Care must be exercised to ensure that laborers do not mix the harvested certified seed with other wheat on the farm.
After a seed crop has been harvested, the seed, if necessary, has to be dried and cleaned.
For wheat seed cleaning, mainly screens, indented cylinders and air screen cleaner are used
Screens separate based on the width and thickness; a width (or diameter) separation is obtained by round screens, while for thickness separation oblong screens are used .
Indented cylinders carry out length separation; the indents (cells or pockets) in the cylinder will, depending on their size, lift the seeds, which fit in the indents.
Air separates seeds according to their behavior in an air stream (seed density) . The most important characteristic is the weight; light particles (dust, chaff, glumes or empty or partly filled seeds) will be lifted, whereas the heavier seed will fall down through the air stream.
It has one air channel to remove light material, one top scalping screen to remove large particles and one bottom grading screen to remove small particles.
Dryer If wheat seed is above 11 to 12 percent moisture, it is dried before it goes into bulk storage or processing. Air-screen cleaner
This is the basic cleaner, usually with two air channels and, preferably, four screens.
The first air channel removes dust and light materials as the seed falls from the feed hopper.
The second air channel removes light seed and materials after the seed passes through the last screen.
Screen configurations vary considerably, one or two top or scalping screens remove particles larger than the good seed, and one or two bottom or grading screens remove particles smaller than the good seed.
Because the average size of wheat seed varies according to the growing conditions, standard screen sizes cannot be recommended..
In general size of Screen aperture for all wheat variety is :
A length separator is almost always used to clean wheat seed. By using the proper machine configuration, shorter or longer undesirable materials (such as broken grains, weed seeds, oat, barley, etc.) are removed. Broken grains and weed seeds, which are shorter than the good seed, are removed by using cylinders with smaller indents.
Larger impurities can be removed by using a cylinder with indents that lift all good seed, but contaminants (wild oats, oats or barley grains and unthreshed glumes) remain in the cylinder.
The gravity separator classifies a seed mixture mainly according to density or specific gravity. It can be used to remove unthreshed glumes and soil particles, which have similar sizes to wheat but different weights.
Another application is the removal of weevil-infested grains from the seed lot and upgrading seed (in order to improve germination).
Furthermore, wild oats and some barley may be removed from the wheat seed lots.
Wheat seed should, if necessary, be treated with the appropriate fungicide to protect the seed and seedling after planting.
Insecticides are sometimes applied to protect seed in storage and in the soil.
Treatments may be applied to protect the seedlings or adult plants against pathogens carried on or in the seed.
In humid and hot climates, seeds may be sealed in vapour-tight plastic bags to maintain viability over longer periods.
In such cases, wheat seed moisture content must be below 9 percent, preferably not over 8.5 percent. Usually, a dehumidified, closed-circuit dryer is used after the seed treatment is applied.
The final step is to weigh the proper amount of seed into the proper kind of bag.
Wheat seed bags should be of a size that fits local farmer needs (seed rates and field size).
Seed yield The average seed yield varies from 30 to 40 q/ha
Seed should be harvested when it reaches harvest maturity, dried to a safe moisture content (if necessary), stored under favourable conditions and protected from damage and pests until it can be planted.
Immature or damaged seed cannot survive long storage periods.
Mechanical injury to seed during harvest or handling makes it more susceptible to deterioration in storage.
seed should be properly dried before going into storage and protected from moisture and high relative humidity.
Fungi (Aspergillusand Penicillium) cause damage to stored seed if seed moisture is high.
High storage temperature has a damaging effect on seed. Stores should be designed so that low temperatures are maintained;
In general, stored wheat seed should be kept at moisture content levels below 12 percent and relative humidity should not exceed 50 to 60 percent. The cleaned, bagged seed should be stored in a dry, insect and rodent proof warehouse.
Effective rodent control (traps and poison) is essential in all seed stores.
A complete programme of exclusion , sanitation and control should be used;
Insects should be controlled by a combination of insecticides and fumigants. Use safest fumigants (e.g. Phostoxin ) because some fumigants (e.g. methyl bromide) will reduce germination.
2. Curative measures Non Chemical control measure.
Temperature : 140C retards reproduction, below 100C kills insects Seed Moisture : seed stored at 10 % moisture content escape from insect. Availability of oxygen :Decrease in oxygen and increase in CO2 is lethal to insects.
Seed health is an important attribute of quality, and seed used for planting should be free from pests. Seed infection may lead to low germination, reduced field establishment, severe yield loss or a total crop failure
In wheat, fungi (Fusariumspp., Tilletiaspp., Drechsleraspp., Septoriaspp. and Ustilagospp.), bacteria (Corynebacterium, Pseudomonas and Xanthomonas) and nematodes (Anguinatritici) are the most important seed-borne diseases due to their worldwide distribution and losses they incur in crop production (Mamluk and van Leur, 1986; Diekmann, 1996a).
Chemical seed treatment is one of the efficient and economic plant protection practices and can be used to control both external and internal seed infection.
It protects young seedlings or adult plants against attack from seed-borne, soil-borne or airborne pests
Meisneret al. (1994) indicated that Vitavax 200 (Carboxin [37.5 percent] and Thiram [37.5 percent]) is an effective broad spectrum seed treatment fungicide, both for externally and internally seed-borne diseases of wheat. Moreover, pre-harvest foliar application of chemicals can also reduce the internally seed-borne fungi and can be combined with seed treatment to produce healthy seed.
Sinclair (1983) cited that foliar spraying of wheat with Benomyl, methyl benzimidazolecarbamate or benomyl plus mancozeb reduced F. graminearum, whereas capatafol and mancozeb reduced Septorinodorum.
Stamina™ A New Fungicide
It inhibits fungal respiration, depriving the pathogen of energy for growth and development
The labeled use rate for Stamina is 0.4 fl oz per 100 lbs of seed.
It has shown to have activity against a broad spectrum of wheat and barley pathogens.
Stamina in combination with Charter® Fungicide Seed Treatment provides protection from a broad range of wheat and barley pathogens.
Single–Kernel Characterization System (SKCS) Method 1. A sample of wheat kernels (12 to 16 grams) is prepared by removing broken kernels, weed seeds, and other foreign material. 2. The sample is poured into the access hopper of the single-kernel characterization system instrument. 3. The SKCS instrument analyzes 300 kernels individually and records the results on a computer graph. Results • Wheat kernel characteristics are analyzed for: kernel weight by load cell, kernel diameter and moisture content by electrical current, and kernel hardness by pressure force. • Averages and standard deviations of these parameters are reported as SKCS results in terms of values: kernel weight is expressed in milligrams (mg); kernel diameter is expressed in millimeters (mm); moisture content is expressed as a percentage; and kernel hardness is expressed as an index of –20 to 120.
Minimum Sample Weight for testing wheat Seeds (ISTA, 2007)
Germination Test ( ISTA,2007 ) Objective: To obtain information with respect to the planting value of the seed and to provide results which could be used to compare the value of different seed lots. Procedure : Replications: Four replication of 100 seeds Substrata : TP, BP, S Temperature: 200C RH : 95±1 First Count : at 4th day Final Count: at 8th day Dormancy breaking treatment: Preheating (30-350 C) First Count Final Count
Seed Moisture Test ISTA,1976 Seed moisture content is one of the most important factor influencing seed quality and storability. Therefore, its estimation during seed quality determination is important. Seed moisture content can be expressed either on wet weight basis or on dry weight basis. Procedure : Three Replication of 4 gram seed . Grinding : Course grinding Either LCT (1030C for 17h; or HCT (1300C) for 2h Use desiccators : 30 – 45 min Calculate moisture content using following formula: W2 – W3 Moisture content (%)= -------------- X 100 W2 – W1
Wheat Varietal Identification Phenol color reaction Extensively used for identification wheat varieties It is easy, quick and reliable test Pieper(1920) was first to use this test Procedure: Soak 50 seeds in water for 16 hrs Place seeds in Petri dishes on 2 layers of filter paper soaked in 1% phenol solution Petri dishes are immediately covered. Observe after 2 hrs and finally at 4 hrs The varieties could be grouped into : Nil, no reaction, Light brown Brown Dark brown Black
Seed Health Testing Direct seed examination Germination test DETECTION METHODS OF PATHOGEN
Detection of Septorianodorumon Wheat (Triticum aestivum)
This method has not been validated for the determination of Septorianodorumon treated seed.
The test is carried out on a working sample of 400 seeds as described in Section 7.4.1 of the International Rules for Seed Testing.
International Rules for Seed Testing ,2008
Method Pretreatment : 10 minutes in 1% (avilable chlorine) sodium hypochlorite. 2.Agar method : Malt agar or Potato Dextrose Agar containing 100 ppm streptomycin sulphate. 3.Incubation: 7 days at 20 ºC in darkness. 4. Examination : After 7 days examine each seed by naked eye for slow-growing circular colonies of dense white or cream mycelium that often covers infected seeds. The reverse of the colony is yellow/brown becoming darker with age. Slow growing, finely tufted, white aerial mycelium of Septoria nodorum covering grain in an agar plate test
Detection of Karnal bunt of wheat, caused by Neovossiaindica Method: Sodium hydroxide ( NaOH) Seed soak.
Procedure: a known quantity of wheat seeds are soaked in a flask/beaker containing 500ml of 0.2 percent NaOH solution for 24 h at 20-300 C.
After 24 h of soaking NaOH is decanted and seeds are thoroughly washed in tap water.
Seeds are spread over a blotter paper so to excess water on the surface of seed is absorbed.
Later seeds are transferred in to a petridish and examined visually aided with light .
The seeds exhibiting jet black shin appearance with hollow or without hollowness are separated and individual seeds are ruptured on a slide in a drop of water and observed for the release of stream of fungal spores under compound microscope
The number of seeds releasing stream of fungal spores are counted and as infected seed and the result are reported in percentage.
Detection of Loose Smut of wheat, caused by Ustilagotritici
Method: Embryo count method.
Procedure: Soak 2000 seeds in 5% NaOH and 0.02% trypan blue solution(one liter) for 24 h at 25-300C.
Pass soaked seed material through 10 mm mesh sieve and retain material in 20 mesh sieve along with showers of tap water.
Collect the extracted embryos in beaker and dehydrate embryos in rectified spirit for 5-10 min.
The hydrated embryos along with chaff etc are taken in a beaker containing 50 ml lactophenol and add to above beaker 100 ml water, stir it well.
Allow to stand for 5 min to settle the chaff at bottom.
Collect the floating in beaker containing 25 ml fresh lactophenol and boil the above material for 2 min.
Pour embryos in to glass dish and arrange in lines along with some lactophenol and observe the embryos under steriobinacular microscope for the presence of mycelium. Mycelium appears as blue thread like knotted structure in the scutellum portion of the embryo.
Total number of embryos and infected embryos are counted and the result are reported in percentage.
Prescribed Seed standard for seed Certification(ISTA) Field Standards
Wheat is a high-volume, low-value crop and has been produced primarily by heavily subsidized government seed programmes.
The private sector, however, may not focus on wheat seed due to its characteristics (self-pollinating, high-volume and low-profit).
To meet the demand for improved seeds of wheat, new improved varieties developed by National Agricultural Research Systems (NARSs) should be multiplied and made available to farmers in the shortest possible time. Appropriate seed production techniques coupled with strict quality control measures ensure that varietal purity and identity is maintained, which is the key foundation of the entire quality seed program.
Seed enterprises consider ‘wheat seed’ to be of secondary importance, since it is a self-pollinating crop and the grain can also be used as seed, farmers tend to re-plant their own seed.
In last ten years significant efforts have been made for commercial exploitation of hybrid wheat through the use of gametocide and CMS lines. Today France and Italy are at the verge of commercial release of such wheat hybrids for grain purposes.