Seed Material

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kheteshwar borawat

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Feb 4, 2009, 1:36:07 AM2/4/09
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Seed Material

Introduction

Seed means seed or any other propagating material used for raising a crop, and it does not mean the particular plant part botanical known as seed.

Types of Seeds

Local Varieties

Local varieties are nothing but traditional varieties but which are susceptible to diseases and pests and are having long duration for maturity. In case of rice - Krishnakatukalu, Basangulu.

High Yielding Varieties

High yielding varieties are dwarf varieties and having short duration with resistant to pests and diseases with maximum yield potential.

Hybrids

A systematic and extensive evaluation of the experimental hybrids, across the country, at the twelve research net work centers has been taken up. About eight hundred experimental hybrids have been evaluated so far. During the wet season ( Kharif), the experimental hybrids are being evaluated at 12 centers, where as during dry season ( rabi ) the experimental hybrids are evaluated in seven centers, located in southern, western and eastern India. Very useful information on performance of hybrids and data on yield and yield components and other auxiliary characters of hybrids across the locations and seasons has been collected over the years.

Genetically Engineered Seeds

One of the major concerns of cultivating hybrid varieties is that farmers can not use seed from the harvest for their next crop and thus have to buy new seed for each crop. More-over, the cost of hybrid seed is 5-20 times more than that of seeds of inbred varieties. Possibilities for true -to- type multiplication of hybrid rice are being explored through two approaches.

  • Production of artificial seeds through somatic embryogenesis and

  • Development of apomictic hybrid rice through wide hybridization and genetic engineering techniques.

Seed Quality

It is the degree of excellence in regard to the characteristics refer to above that determines the seed quality. If the seed lots posses high genetic purity and high germination percentage and a minimum of inert, weed and other crop seeds and are free from diseases., it is said to have high quality .Generally the standards fixed for certified seeds are considered quality standards. It implies that a if a seed lot meets the certification standard, it is good quality seed and if does not meet the certification standards, it is obviously of a lower seed quality.  The characteristics of good quality seeds include high yield, high physical purity, high seed germination and vigor, optimum seed moisture and good seed health.

Categories of Seed

Breeder Seed

Breeder seed is seed or vegetative propagating material produced by or under the direct control of the sponsoring plant breeder. It is the basis of the first and recurring increase of foundation seed.

Foundation Seed

It is obtained from breeder seed by direct increase and is the source of registered and or certified seed. Foundation seed is produced on experimental stations of Agricultural Universities and Government forms.

Certified Seeds

  • Certified seed is produced from foundation or registered seed. It is so known because it is certified by a seed certifying agency.

  • The certified seed is annually produced by progressive farmers according to standard seed production practices. Certified seed is available for general distribution to farmers for commercial crop production.

Public Hybrid

The hybrids developed by Govt. agencies or Govt. Institutions and Agricultural Universities are called public hybrids.

F1 Hybrid

The resultant seed obtained from crossing of two genetically dissimilar parents is called F1 Hybrids.

Seed Viability

Seed viability is defined as " The capability of a seed to show living properties like germination and growth" or it is represented by germination percentage which expresses the number of seedlings that can be produced by a given number of seeds.

Factors Responsible for Reducing Viability

  1. Factors which are favorable for germination of seed reduce viability. For example water, high humidity, high temperature etc.

  2. Stage of maturity when harvested. Less matured seeds have low viability.

  3. Incidence of storage pests and diseases. If the seeds are eaten or damage by insects and non-insects, their viability is less.

  4. Physical injuries during storage.

Seed Dormancy

It is a condition of a seed in which it is temporarily inactive. It does not die but does not grow also. The dormancy of seeds varies widely from seed to seed. Some seeds remain viable only for few days (40 to 50 days). While some seeds remain dormant for few years. It is this dormancy which is to be preserved during storage. Whether the dormancy is less or more care has to be taken during storage specially for seeds which have less dormancy.

Intensity of Dormancy

This refers to the level of breaking dormancy by artificial means, i.e., based on the germination percentage after heat treatment for four days at 50 degrees centigrade, and the rice varieties classified based on germination percentage as follows

Strongly Dormant

Varieties in which 50% of dormancy is broken after 4 days of heat treatment.

Moderately Dormant

Varieties in which 50 to 79% of dormancy is broken after 4 days of heat treatment.

Weakly Dormant

Varieties in which above 80% of dormancy is broken after 4 days of heat treatment.

Seed Storage

need for Seed Storage

  1. Seed produced in one season is used in the next season. Till that time it has to be stored.

  2. Extra unused or unsold seed has necessarily to be stored.

  3. In research plant breeders have to store seeds of variety of crops for 5-10 years to maintain germplasm.

Technique of Storage

Technique of storage involves following steps:

  1. To control environmental factors temperature & humidity. High temperature and high humidity reduce the viability of seed. The temperature should be less than 30o C and humidity 50-60 %. The seed should be stored in cool dry places.

  2. Moisture content of seeds. The seed should be dried properly in the sun or by mechanical driers as to bring down moisture content within range of 8 to 9 per cent.

  3. Cleanliness: Store room/godown should be properly cleaned, it should be painted with while colour and sprayed with Malathion 50EC insecticide.

  4. Care During Storage: The seed should be inspected every after 15 days and manipulated accordingly. If there is any incidence of storegrain pests fumigation should be done with Aluminium phosphide tablets 2 to 3 tablets per tonne. Ethylene dibromide 32 gm per cubic meter space. After fumigation there should be good ventilation. The godown should be disinfected every after 3-4 weeks with sprays of Malathion 50 EC. The godown should always be kept clean.

Seed Treatment

Seed treatment refers to the application of fungicide, insecticide or a combination of both to seeds, such as to disinfect and disinfest them from seed - borne or soil-borne pathogenic organisms and crop pests both in field and in storage. It also refers to the subjecting of seeds to solar energy exposure, immersion in conditioned water etc.

Benefits of Seed Treatment

  • Seed treatment improves the germination of seed.

  • Good establishment of healthy and vigorous plants.

  • Increase the production.

  • Seed does not rot after sowing or plant does not die.

  • It helps to save the expenses of disease control.

  • It helps to control the seed borne diseases

  • Protection of seeds in storage.

Dry Storage

For species where dormancy is naturally of short duration, it is often sufficient to store the samples in a dry place for a short period.

Pre-Chilling

The replicates for germination are placed in contact with the moist substratum and kept at low temperature for an initial period. Agricultural and vegetable seeds are kept at a temperature between 5 and 10 degrees Centigrade for an initial period of upto 7 days. In some cases it may be necessary to extend the pre-chilling period or to re-chilling.

Pre-Heating

The replicates for germination should be heated at a temperature not exceeding 40 degree C, with free air circulation, for a period of upto 7 days before they are placed under the prescribed germination conditions.

Light

The test should be illuminated during atleast 8 hours in every twenty four hours cycle and during the high temperature period when the seeds are germinated at alternating temperatures. The light intensity should be approximately 750 - 1250 lux from cool white lamps. Illumination is recommended especially for certain tropical and sub-tropical grasses.

Eg. Chloris gayana, Cynodon

Seed Treatment BY APPLICATION OF CHEMICALS

Several insecticides and fungicides are used in seed treatment to protect the seeds from pests and diseases.

QUANTITY AND METHOD OF SEED TREATMENT FOR DIFFERENT CROPS

  CROP CHEMICAL QUANTITY

For 100 Kg seeds

(in GRM)

METHOD
1 Sorghum Thiram 100 Paste form
2 Bajra Thiram 100 Paste form
    Captan 300 Dust form
3 Rice Ceresan 2.5% 60 Solution
    Organo-mercury 250 Dust form
4 Cotton Captan 250 Dust form
    Thiram 100 Paste form
5 Groundnut Thiram 125 Paste form
    Captan 250 Dust form
6 Sun Flower Captan + Thiram 150+150 Dust form
7 Tur Thiram 100 Paste form
8 Gram Captaphol 250 Dust form
9 Cowpea Thiram 250 Dust form
10 Green gram Thiram 100 Paste form
11 Wheat Thiram 100 Paste form
12 Cole crops Thiram 250 Dust form
13 Tuber crops Thiram 250 Dust form
14 Gourds Thiram 250 Dust form
15 Bhendi Thiram 100 Paste form
    Captan 250 Dust form
16 Beans Thiram 100 Paste form
17 Lucern Thiram 100 Paste form

 

Seed Germination

Seed germination is the resumption of growth by the embryo and development of young plant from the seed.

Germination, in a laboratory test, is the emergence and development from the seed embryo of those essential structures which, for the kind of being tested, indicate the ability to develop into a normal plant under favourable conditions in the soil.

Treatments for Promoting Germination

  • For reasons such as physiological dormancy, hard seededness, inhibitory substances a considerable number of hard or fresh seeds may remain at the end of the germination test.

  • When a proportion of fresh or dormant seeds remain at the end of the test period, complete germination can often be obtained by re-testing after a period of dry storage. The following methods may also be used to induce germination.

Methods to Overcome Physiological Dormancy

  • Dry storage

  • Pre-chilling

  • Pre-heating

  • Light treatment

  • Potassium nitrate ( KNo3) treatment

  • Gibberellic acid (GA3) treatment

  • Sealed polythene envelope treatment.

Methods of Removing Inhibitory Substances

  • Pre - washing

  • Removal of structures around the seed.

  • Disinfection of the seed.

Methods for Removing Hard Seededness

  • Soaking

  • Mechanical scarification

  • Acid scarification.



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Have a lot of fun and success.
yours kheteshwar
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