बाजरेे का संकर बीज उत्पादन

Pearl millet is a highly cross-pollinated crop due to its protogyny condition of flower. In this condition stigma of the flower emerges first and mature before pollen shedding this condition of flower promote cross pollination. This nature of flowering facilitates the breeding of hybrids and open-pollinated varieties (OPVs).

For hybrid seed production two methods are used first parental line growing in crossing block and harvest seed. The resultant seed contained approximately 40% hybrid seed when the two parental lines had synchronous flowering. This is called chance hybrid.

In second method cytoplasmic-nuclear male-sterility lines like male-sterile lines Tift 23A and Tift 18A are used. These lines shows short stature, profuse tillering, uniform flowering and good combining ability are used in current breeding programme of pearl millet. In hybrid seed production chain, nucleus seed, breeder seed, foundation seed and certified seed are produce.

Certified seed is the progeny of foundation seed and must meet the standards of seed certification prescribed in the Indian Minimum Seeds Certification Standards, 1988. Certified seed production is organized through State Seeds Corporations, Departmental Agricultural Farms, and Cooperatives etc.

The efforts of the State Governments are also supplemented by NSC which produces seed of varieties of national importance. The production of certified seed by NSC and State Seed Corporations is mainly organized through contractual growing arrangements with progressive farmers.

The production and distribution of certified quality seeds is primarily the responsibility of the State Governments. The private sector also plays a very important role in the supply of quality seeds (mostly hybrids) of pearl millet.

Hybrid Seed production of Pearl Millet

Isolation distance:

As pearl millet is a highly cross pollinated crop-recommended isolation distance should be followed strictly. The seed crop must be sufficiently isolated from near by fields of the same crop as per the requirements of certification standards.

Seed village approach is commonly followed for certified seed production to avoid isolation problem. Even after the seed crop is harvested, effective isolation of seed from different varieties is essential to avoid mechanical contamination

Land preparation:

Cultivation of field two times (cross ploughing) and harrowing once is sufficient to bring field to fine tilth. Use of plank tied behind the cultivator may be necessary to break large clods and more harrows may be required in case of fields infested with weeds.

Planting method:

Planting is done either by direct sowing of seed or transplanting the seedlings raised in nursery. Generally, tractor or bullock-drawn seed drills or bullock plough is used for sowing. A-lines are planted by machine-drawn seed drill and R-lines are planted manually by hand dibbling in rows marked with stakes. Sowing equipment needs to be thoroughly cleaned to avoid contamination during sowing.

Transplanting:

Transplanting enables easy adjustment in flowering time of parental lines in case they have large differences for flowering time. Transplanting saves expenditure on weeding and irrigation. It also saves time when field is occupied with any other crop. Transplanting requires 30-40% less seed than direct sowing and proper plant stand is achieved with required spacing.

The parents of hybrid are sown in a nursery bed raised 10 cm above the ground level. Seed should be sown 1.5 cm deep to facilitate better germination and safe uprooting of seedlings for transplanting. Seed is sown in rows spaced 10-15 cm apart. Seedlings are transplanted in the field when they are 18-20 days old. Transplanting of seedlings older than 20 days might result in reduced tillering and low seed yield.

Field layout and row ratio:

Ratio of male and female lines depends on height and pollen producing ability of pollinator line. Standard female: male row ratio of either 4:2 or 8:2 is followed for certified seed production. Most common ratio is 8:2 due to ease of management.

To ensure longer duration of pollen availability, staggered planting of male parent at more than one date is followed with a minimum gap of 3 days between two plantings of male parental lines. All sides of field should be covered with 2-4 border rows of male line.

Seed rate:

The seed rate depends on planting method and row-to-row and plant-to plant spacing. General seed rate recommendation for foundation seed production is 3 kg/ha of A-line and 4 kg/ha for R-line and OPV. Seed rate of 3 kg/ha of A-line and 1 kg/ha of R-line is generally

Spacing:

Optimum population is 1,00,000 plants per hectare and hence it is recommended to follow 50 cm row-to-row and 20 cm plant-to-plant spacing in certified seed production. However, in nucleus and breeder seed production row-to row spacing of 75 cm and plant-to-plant spacing of 20-25 cm is followed to facilitate closer look at individual plants in order to identify and rogue out off-types, including pollen shedders in A-lines. Such spacing also allows better expression of plants and facilitates rouging extreme phenotypes.

Fertilizer management:

Adequate amount of nitrogen, phosphorus and potassium is essential for proper growth and development of the crop. It is recommended to apply FYM @ 8-10 tons/ha and NPK @ 100:60:40 kg/ha. Basal dose of 40 kg N/ha is applied, and remaining nitrogen should be applied at tillering stage. Soils should also be analyzed for micronutrients, especially zinc, sulfur and boron, and those found deficient should be amended through proper micronutrient management.

Water management:

Most of pearl millet seed production is taken during off season (January to April) which is rain-free period. Therefore, access to irrigation is essential to obtain good seed yields. The most critical stages of irrigation are tillering, flowering and seed development.

The frequency of irrigation and amount of water supplied depend upon physical texture of the soil and crop requirements. Adequate soil moisture is also necessary for uniform seed germination in order to obtain good plant stand and high seed yields.

Weed control:

Production of high seed yield of high quality requires good weed control in the seed production plots. In addition to reduction in seed yield, weeds are often a source of contamination by way of admixture at the time of harvest. Weeds must not be allowed to flower or set seed in any case. Hand weeding, intercultural operations or chemical is necessary to control weeds.

Pre emergence spray of Atrazine @ 1g/litre controls broad-leaf weeds effectively. 10. Disease control: Effective control of all diseases is essential to produce a healthy seed crop. Diseases like downy mildew (Sclerospora graminicola (Sacc.) Schroet), blast (Pyricularia grisea (Cke.) Sacc.), and ergot (Claviceps fusiformis ) cause heavy yield reduction and affect seed quality also.

Adoption of appropriate schedules of plant protection and rouging of diseased plants and panicles from time to time are essential to further check the spread of diseases. Following are the control measures for important diseases of pearl millet.

Insect-pest control:

Major pests of pearl millet are armyworm (Spodoptera frugiperda), blister beetle (Psalydolytta fusca Olivier) and shoot fly (Atherigona soccata Rondani) that need proper control to avoid yield losses in production plots. The following control measures against each of these pests include:

Male-female flowering synchronization:

Synchronization of flowering of A-line with R-line in certified seed production plots is essential in order to ensure pollen availability in the R-line when stigmas emerge in the A-line. Synchronized flowering results in good seed set in A-line and higher yields in production plots. The A- and R-line may differ for flowering Synchronization of flowering of A- and R-lines can also be enhanced by 

• by spray of  urea- Hastening of flowering time by 6-8 days can be achieved by 3-4 sprays of 4% urea at 2-3 days interval at boot leaf stage.
• by staggered planting - If the difference in flowering time of parental lines is more, a practice of staggered sowing is followed. In which  male parental line planted at different dates.
• by Jerking method-  Removal of first tiller or ear of first tiller for synchronization of flowering of the parental line called Jerking.

Roguing:

The process of removal of pollen shedders from A-lines and off-types from parental lines in seed production field is called roguing. Pollen shedders are male fertile plants in an A-line with similar morphology. Pollen shedders in A-line are results of mutations or mechanical mixtures. Off-type plants obviously differing in characteristics such as height, flowering time, colour of foliage, leaf size, shape, and orientation, tillering, panicle size, or any other morphological characteristic or diseased plants.

It may arise through mechanical mixture or out crossing and rarely as mutants. Adequate and timely rouging constitutes the most important operation in seed production. Rogues differing from normal plants in phenotypes should be pulled out and discarded at the earliest possible stage of plant growth, before flowering to avoid genetic contamination.

Roguing at maturity is also necessary to remove off-types not distinguishable earlier, and contaminants affecting the physical purity of seed. Roguing and sorting out of harvested panicles may be necessary in case of diseased panicles.

Field inspection:

Field inspection is a necessary monitoring protocol and is a prerequisite to ensure quality seed production. It involves recording cultivar identification, crop purity, disease incidence, general stand assessment, cultural practices, previous crop, dates and number of inspections, and roguing details. This is followed by recording of established plant population, species and cultivar purity and the establishment of rejection/selection criteria. A minimum of four inspections are made at different stage of seed production .

(i) The first inspection is made before flowering preferably within 30 days after planting in order to determine isolation, volunteer plants, outcrosses plants, planting ratio, any error in planting, incidence of downy mildew and other relevant factors.

(ii) The second and third inspections are made during flowering to check isolation, off-types, pollen shedders, downy mildew/ green ear and other relevant factors.

(iii) The fourth inspection is made at maturity but prior to harvesting in order to determine the incidence of downy mildew/green ear, ergot and smut and to verify true nature of plant and other relevant factors. When the seed production field does not meet the specified certification requirement, the options are whether whole field or part of the field is recommended for grow out test (GOT).

The area not meeting the requirements is harvested as seed of doubtful purity, kept separate, and final decision on the disposition of seed is made by observing genetic purity report. Plants of male line are chopped to avoid contamination. At least 25% of fields are inspected to validate the submitted male chopping report and to ensure that chopped male plants were properly destroyed or taken off the production field.

Harvesting and drying:

The appropriate time of harvest to ensure maximum seed yield and quality is of great significance. Fully mature seed is easily harvested and cleaned with minimal harvest losses. Delayed harvesting may result in increased losses due to lodging and seed shattering. Sun drying of seeds on clean threshing floor may be necessary to reduce moisture content, preserve viability and vigour and improve storage quality. Drying of seed to recommended moisture level of 12% is necessary to preserve its viability and vigour.

Precautions:

• In certified seed production, R-line should be harvested first.
• Field should be thoroughly checked before harvesting A- line to avoid mixture
• Ensure that the drying yard is clean and free from any pearl millet or other crop seed
• Avoid making big heap at high moisture as it may deteriorate seed vigour.
• Panicles should be dried to 12% moisture level • Harvested material should be double checked properly.

Threshing:

Care must be taken during threshing operations to avoid any chance of mechanical mixture. Threshing should be done lot wise. Checking and cleaning of threshers before use is a must to keep seed free from other seeds and Seeds should be cleaned before dispatching to processing plant by winnowing /using screens to remove chaffy /unwanted materials.

Seed certification:

Seed certification consists of several quality control measures that ensure supply of quality seeds to farmers. For this different following test were conducted

• For Genetic purity- Grow out test
• Germination test
• Physical purity test

Seed standards for Pearl Millet

Field standards

References

1. R.L. Agarwal, Seed technology, Oxford and IBH publisher New Delhi, second edition (2008).
2. P. K Agarwal (2015). Principles of Seed Technology, publisher Indian Council of Agricultural Research New Delhi.
3. D., Khare and  M.S., Bhale.  Seed technology(2000). Scientific Publishers.

Authors

Turfan Khan¹, Ganga Ram Mali², Dr. Pradeep Pagaria³ and Chetan Kumar Saini⁴

¹Farm Manager , Krishi vigyan Kendra Gudamalani, Barmer-II (Rajasthan)-344031

²Programmae Assistant, Krishi vigyan Kendra Gudamalani, Barmer-II (Rajasthan)-344031

³Senior Scientist and Head, Krishi vigyan Kendra Gudamalani, Barmer-II (Rajasthan)-344031

⁴Msc, Research Scholar, Department of Statistics, JNKVV, Jabalpur  ( MP)- 482004

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