Source seed production technology in maize by jiban shrestha, nepal agricultural research council, national maize research program, rampur, chitwan, nepal
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Source seed production technology in maize by jiban shrestha, nepal agricultural research council, national maize research program, rampur, chitwan, nepal






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Source seed production technology in maize by jiban shrestha, nepal agricultural research council, national maize research program, rampur, chitwan, nepal Source seed production technology in maize by jiban shrestha, nepal agricultural research council, national maize research program, rampur, chitwan, nepal Presentation Transcript

  • SOURCE SEED (BS, FS & IS ) PRODUCTION OF MAIZE Jiban Shrestha Scientists (Plant Breeding and Genetics) Nepal Agricultural Research Council National Maize Research Program, Rampur, Chitwan, Nepal
  • Biology of the maize plant: The maize plant has separate male and female flowers (Monoecious Plant). The location of the tassel (male flower) at the top of a relatively tall plant and its separation from the female flower promotes cross- pollination between plants. One tassel may produce up to 25 million pollen grains. How to produce maize seed: To maintain the genetic purity and characteristics of a variety cross-pollination between different maize varieties must be prevented. Isolating the seed production field from other maize fields helps achieve this.
  • Seed a link between plant generation a carrier of gene a technology most transportable, storable, and functional unit Quality seeds central to agricultural production and productivity a source of all food with plant origin Seed is fertilized mature ovule covered by a protective coat/coats which is viable and can germinate under favorable environment conditions
  • Types of seed 1. Nucleus Seed 2. Breeder Seed 3. Foundation Seed 4. Improved Seed Nucleus Seed Nucleus seed is also called progenitor of breeder seed. There is direct involvement of breeder in nucleus seed production. Selection is done with certain rules. Nucleus seed is produced in very less quantity.
  • Breeder Seed The progeny of nucleus seed. Produced at one place only in the control of breeders through positive selection process with very strong rouging.  Golden yellow tag is used To maintain the highest level of purity, the breeder's seed plot should be small and manageable. Acceptable Standard deviation can be ±0.7sfor quantitative traits of plants and ears. Coefficient variation can be ±3% for qualitative traits of plants and ears
  • Ways/Methods of Breeder Seed Production: 1. Isolated mass selection plot Parental seed should be planted in isolation to obtain about 8000 plants. The entire field can be stratified in grids of 16 plants each. Before pollen shed, about half of plants in each grid which do not fit the description of variety are detasseled. Before harvest 2-3 of most acceptable plants in each grid are selected and tagged. At harvest ears from only one of the tagged plants that are acceptable color and kernel texture is selected from each grid. A total of 500 ears are selected in this manner from the parental seed. Ears of plants that were not detasseled and that fit well the definition of the variety provide the breeder seed to produce the foundation seed. Ears from the detasseled plants may harvested for commercial gain.
  • 2. Half sib crossing block It requires isolation and can be initiated in the first generation of breeder seed increase. The 500 ears selected from the bulk seed increased are shelled separately, and planted as individual female entries in a half sib crossing block, in which every two female rows are flanked by one male row. Male row consists of a balanced mixture of an equal amount of seed from each ear. Before anther dehiscence all plants in the female rows are detasselled. Roughing of the off types and the undesirable plants can take place in male row to leave no less than 70 of the tassels intact to ensure an adequate pollen supply.
  • Approximately half the numbers of female rows are selected as most desirable and representative of the variety. Selection of the family is aided by the reference male row at its side, which represents the mean of the variety. From each selected female row or family, 2-3 of the best ears from the best plants are selected to recover approximately 500 ears as parents for the next increases of the breeder seed. Rests of the ears from the selected female rows are harvested as breeder seed for the production of foundation seed. Thus the system is maintained. Because of the utmost important of maintaining the uniformity of the breeder seed, the seed of origin, it is imperative that this be done by the breeder in one location only, and the soil condition and management should be uniform.
  • Foundation Seed The progeny of breeder seed. Produced through negative selection process with strong rouging. white tag is used. Certification process used for the foundation seed. Up to 10-15% of the off-type plants can be rogued before flowering. Roguing for ear and seed traits is done at or after the harvest. Acceptable Standard deviaton can be ±1.55sfor quantitative traits of plants and ears. Coefficient variation can be ±5% for qualitative traits of plants and ears
  • Ways of Foundation seed production The second seed increase serves to produce foundation seed. Foundation seed is obtained by planting the breeder seed in isolation. Selection is not possible nor desirable at this stage, but of off types plants should be rouged before pollen shed, and more pollination is allowed. In any event the area of production should be uniform to minimize undesirable variation.
  • Improved Seed The progeny of foundation seed. Produced with medium rouging. white tag with blue border is used.  Certification and Truthful label process used for the improved seed. Up to 5% of the off-type plants rogued before flowering. Roguing for the ear and seed traits at or after the harvest. Acceptable Standard deviaton can be 1.96sfor quantitative traits of plants and ears. Coefficient variation can be ±8% for qualitative traits of plants and ears
  • Ways of Improved Seed Production In the third seed increased improved seed is produced from foundation seed in the same manner as described above. Again selection is neither necessary nor desirable, but roughing is essential. An appropriate area to produce sufficient seed for current demand, plus necessary carry over stock, is planted with foundation seed in isolation and open pollination is allowed. Obvious off types plants are roughed before dehiscence to maintain the integrity of the variety.
  • Because of the greatly increased area needed to produce the necessary quantity of seed at this phase it will be necessary to use several different locations, farmer participation as contract growers is essential. The close collaboration of the research staff and the farmers during variety evaluation and verification trials is especially helpful here since it will allow the researchers to identify the most reliable farmers for this valuable function. The integrity and the quality of seed for the commercial planting will depend on the integrity and quality of these farmers, the producers of improved seed.
  • Isolating a seed production field: Isolation of a seed crop can be done in four ways: 1. By space or distance - maintain a distance of at least 200 meters between the seed crop and any other maize field. 2. By time - plant your seed crop 20 – 25 days earlier or later than neighboring maize fields.
  • 3. By certified seed barrier (Boarder rows)– a barrier of genetically pure seed of the same variety may be planted within the isolation distance of the seed production field. For example: Area (ha) of the seed field No. of boarder rows of the Male Parent 4 8 12 16 Isolation Distance in meter 200 190 180 170 1 150 140 130 120 5 50 40 30 20 13
  • 4. By natural barriers – seed production plots can be established on land isolated by natural or artificial forests. Distance and time isolation are most commonly used. The goal is to have no other maize variety shedding pollen nearby when the seed production field is flowering. Wind may carry pollen further than 300 meters. Thus, if there are constant strong winds in one particular direction, the distance to the next maize field should be at least 400 meters.
  • How to select a suitable field: • Check with neighbors when and where they will plant their maize so that you can select a field that is isolated. • Choose a field where no maize has been grown during the previous year to reduce the possibility that last year’s maize crop may germinate and cross-pollinate your seed maize. • Farming communities may want to produce the seed of one variety for the entire community in one single field. (eg. CBSP).
  • How to manage your seed production field: • Prepare the soil in your field at least two weeks prior to planting. If there are any grains from previous maize crops left in the soil, they may germinate in these two weeks and you should remove them when you plant your maize seed crop. • If possible, plant your maize seed crop early. • Use 10 - 15 % less plant population than maize grain production plot. • Planting in straight rows will help facilitate various seed production operations. • Remove weeds in time.
  • Rouging  During the season, carefully examine your maize seed crop:  Plants that look very different ( taller, very dwarf, diseased, weeds) or flower much earlier or later than the majority of plants in the field. These plants are called off-types and they should be removed (Rouged out) before pollen shedding starts.  If off-type maize plants are detasseled, seeds from such plants should not be used.
  • Number of plants per hectare Row width in cm 50 60 70 75 Spacing between plants (in the same row in cm) 35,000 57 48 41 38 40,000 50 40 35 33 45,000 44 35 31 30 50,000 40 30 28 26 55,000 36 37 25 24 60,000 33 25 22 21 65,000 31 22 20 19 70,000 28 21 19 18 Row width and spacing between the plants in the row according to the desired density In seed production, 75cm × 30 cm spacing or 45,333 plant population/ha or Seed rate-17kg/ha is needed
  • Standards for maintaining varietal uniformity Maize seed should meet the following standards Minimum field standard Minimum crop standard Minimum seed standard
  • Minimum field standard Land requirement:Free fromVolunteer Plants -Crop rotation to minimize volunteer maize plants and reduce the need for roguing. Maintaining isolation distance or time Isolating a seed production field: 1.By space or distance 2.Bytime-plant your seed crop 20-25 days earlier or later than neighboring maize fields.-Silking period should not coincide with corn in near by fields
  • Minimum number of field inspections First inspection-Before flowering Verification of seed source, isolation distance and suggestion for rouging. Second inspection-After complete flowering Counting, field certification/rejection Third inspection-Cob inspection at threshing floor Minimum crop standard off-type plants Less than 10-15 & 5% off-type plants in foundation and improved seed respectively No any designated diseases and weed plants
  • S. N. Parameters Standards Foundation Seed Improved Seed 1 Pure seed (Minimum) 98.0 % 98.0 % 2 Inert matter (Maximum) 2.0 % 2.0 % 3 Other crops seed (Maximum) 5/kg 10/kg 4 Other varieties seed (Maximum) 10/kg 20/kg 5 Weed seed (Maximum) 0 0 6 Germination (Minimum) 85 % 85 % 7 Moisture (Maximum) 12.0 % 12.0 % Minimum Seed Standard Seeds hould be obtained from reliable source and seed replacement should be done every year to ensure good quality seed production
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