- The ovule after fertilization develops into the seed with its coats completely fused together with the developing ovary wall or pericarp. The rice grain has the following structures.
The Pericarp or Fruit Coat
- The pericarp is made up of distinct layers of quadrangular cells which forms the epicarp. These cells have slight thickening and are followed by cells which are much compressed and form the mesocarp consisting of two to three layers.
- The endocarp is single layer of tube cells. The colour in the rice grain is found in the pericarp layer in the mature stage.
The Seed Coats
- Due to the pressure brought out by the developing seed on the pericarp, the testa and tegmen become much pressed down and out of shape. A few layers of such cells below the pericarp can be diagnosed as the integuments of seed coats.
Aleurone Layer
- A prominent layer of rectangular cells which contain protein lies next to the seed cents. This layer is known as the aleurone layer. This layer in rice is not coloured unlike in the case of maize.
- It has been observed that in coloured varieties of rice, the aleurone layer is thicker than in the white rice varieties. The coarse rice generally have a larger aleurone layer than the finer rice. It has also been found that in poor soils, the aleurone layer is thin and improves in thickness with the fertility of the soil and manure.
The Endosperm
- The entire mass of tissue below the aleurone layer is made up of cells which contain plenty of starch grains and these form the endosperm.
The Embryo
- The scutellum has an upper free part which has a flesh projection known as ventral scale. Below this upper ventral scale and almost at the middle of the free part there is another out growth which can be called as the 'inner ventral scale' and this inner ventral scale is peculiar to rice embryos only.
- On the surface of the embryo this out growth along with the epiblast forms a continuous covering around the plumule. The structure between the scutellum and the plumule is the mesocotyl.
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- 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.
Eg: I.R -64, I.R - 36, I.R - 50.
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.
- As a result of concerted, goal oriented, time bound and co-ordinated efforts for the first time in the country, four rice hybrids were released for commercial cultivation during 1994, by the state variety release committee. These are APHR-1 and APHR- 2 for the Telangana and Rayalaseema regions of Andhra pradesh, MGR-1 for the Tamilnadu state and KRH-1 for Karnataka state. Subsequently two more hybrids, viz., CHRH -3 and DRRH-1 were released recently.
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.
Production of Artificial Seeds And Mass Propagation of True- Breeding Hybrids
- Artificial seeds, consisting of somatic embryos, enclosed in a protective coating, are being proposed as low-cost, high-volume propagation system. The objective is to produce clonal seeds at a cost comparable with that of producing hybrid seed by conventional methods. Artificial seeds can be produced through somatic embryogenesis. This is the process by which somatic cells develop through the stages of embryogeny to give whole plants without gametic fusion. Somatic embryogenesis has been reported in more than 150 plant species. Somatic embryos have been induced from a variety of plant tissues, such as germinating seedlings shoot meristems, young inflorescence, nucellus, leaf, anther, root and others.
- Artificial seed technology involves various steps for the production of somatic embryos and their utilization as commercial propagules.
- Optimization of somatic embryogenesis system from cultured cells
- Optimization of embryo maturation.
- Automation of embryo production.
- Production of mature synchronized embryos.
- Encapsulation of embryos with necessary adjuvants.
- Coating of encapsulated embryos.
- Optimization of green house and field conditions for conversion of embryos into plants. And
- Delivery system for artificial seeds.
Tissue Culture
- "It is the process of growing tissue or cells which are exercised from healthy plants. These tissues are grown on nutrient medium under aseptic conditions."
- It is also called as micro propagation.
Tissue culture involves several techniques which are
- Anther culture
- Embryo rescue or ovary culture or Embryo culture.
- Protoplast culture and protoplast fusion.
- Somatic embryogenesis.
- To develop a straight variety or true to type variety in crop plants, pure line selection method is adopted. In this method the seeds of pure lines are selected from homogeneous population of a particular crop and multiplied in the next season. This multiplication process is conducted in different co-ordinated centers and performance of the pure lines is tested. If the performance is good then the state varietal release committee or central varietal release committee releases the variety of that particular crop.
- The seed supplied from Agricultural Research Stations, Department of Agriculture, or A.P. State seed corporation is not adequate to meet the requirements of the farmers. So the private seed producers are actively engaged in multiplication and supply of seed to the farmers. But the cost of seed is some times high and the quality also is not maintained. Hence, the farmers are motivated to develop their own seed in respect to varieties.
- A seed village concept was introduced and the farmers were encouraged to develop their own seed. In this process the farmer is supplied with limited quantity of foundation seed or certified seed by Research stations or A.P State seed corporation. The farmer will grow variety with the seed supplied in a limited area with good management practices of both plant husbandry and plant protection. He is also provided with information of the characters of the variety like duration, grain type, the time of panicle initiation etc. He observes the crop from time to time, and the off-types will be removed as and when noticed. He maintained a homogenous type of plants having the varietal characters . while harvesting he eliminates 1 meter crop from all sides of the field to avoid contamination from other varieties grown in neighbor hood and threshed, separately with all the care to prevent admixture of other varieties in threshing floor.
- Like wise care will be taken during storage to maintain purity. Such seed will be used continuously year after year for the period of 3 to 4 years. Such seed can also be spread to the co-farmers interested in that specific Variety. After 4 years the farmer can again secure foundation seed or certified seed from the Research station. If it is practiced by atleast 25% of the farmers there will not be any scarcity for pure good seed.
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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.
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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.
- The duration of seed viability of rice varieties depends mainly on the following aspects.
- Seed moisture % at the time of storage ( 10 to 12% is desirable).
- Storage conditions.
- Weather conditions ( relative humidity, rainfall)
Seed Moisture
- The formation of germination inhibitors was accelerated under reduced oxygen tension and thereby the water content of the seed is increased which deteriorates viability.
Storage
- The embryos and endosperm of seeds of different ages were found to respire, the rate being higher in fresh seeds then in older ones. Thus, the old seeds are living but failed to germinate.
- The germination and viability of the rice seed are related to the formation of inhibitors during storage.
Weather Conditions
- Higher relative humidity and rainfall during the storage periods will deteriorate the seed viability .
- The paddy seed viability depends on the weather conditions. The seed viability deteriorate very fast during monsoon season.
- Due to this, the seed harvested during rabi season do not retain its viability upto the next rabi season, because it passes through the monsoon weather conditions i.e., from June to October months, where as the kharif harvested seed retains its viability till the next kharif season.
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Seed Dormancy
- Seed dormancy refers to the resting stage of embryo with low germinability of viable and freshly harvested grains. It is also defined as inability or failure of perfectly matured seed to germinate even when placed under conditions favourable for germination.
- Seed dormancy is an important varietal trait in tropical rice where rain fall and high humidity are of frequent occurance during the maturity and harvest periods. Without dormancy, seed would germinate on the standing crop.
Classification of Dormancy
Seed Dormancy at Maturity Stage
- Strong seed dormancy at maturity of the crop is a most desirable trait for all the kharif varieties. Some of the rice varieties ( Masuri, I.R -50) have little or no seed dormancy and in periods of wet weather at harvest time, the seed may germinate on the panicle itself.
Duration or Length of Dormancy
- This refers to the period from harvest time to the time when the seeds have broken their 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.
Factors Influencing Dormancy Period
Climatic Conditions
Temperature
- Rice produced during the cloudy wet season ( kharif) has a strong dormancy and longer duration of dormancy than that of produced during the summer dry season ( rabi).
- This is mainly due to the temperature differences ( higher temperatures in rabi) during the ripening stage of the crop.
Relative Humidity
- Higher R.H in atmosphere at maturity stage also increase the degree of dormancy.
Age of Seeds
- A wide variation in maturity of seeds can be observed within a hill, i.e., between the mother tiller to tertiary tillers. Similarly there is about 7 to 10 days difference in the maturity of individual seeds within the same panicle.
- The seeds in the upper portion of the panicle have earlier maturity than the lower portion of the panicle. So the duration, the dormancy of the individual seed varies with in the hill and also within the panicle.
Genetics of Dormancy
- Genetically dormancy is dominant over non-dormancy. Dormancy is inherited independently and can combine with early maturity, photo sensitivity and also with a range of grain types.
Mechanism of Dormancy
- Dormancy is the resultant of the slowing down effect of the metabolic process during seed maturation and also by the slow oxidation of the hormone IAA ( Indole Acetic Acid).
- Hence, it is essential that any treatment aimed at breaking seed dormancy should hasten the rate of oxidation. Respiration is a strong competitor for the oxygen available for the dormancy breaking reaction.
Breaking Seed Dormancy
- Among the several methods available the most suitable method to break seed dormancy at farmers level is nitric acid treatment. - Soaking the seed in o.1 N nitric acid i.e., 6.3 ml per lit. of water for 12 to 24 hours effectively breaks the seed dormancy, where as the varieties like MTU-1001 which is having 8 weeks and above dormancy duration should be treated with higher nitric acid concentration i.e., 10ml per lit. of water.
- The seeds can be utilized for sowing immediately after the treatment or they can be dried thoroughly and can be utilized later for sowing.
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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
- Prevention of spread of plant diseases.
- Seed treatment protects seed from seed rot and seedling blight.
- Improves germination.
- Provides protection from insect pests.
- Controlling soil insects.
Seed Treatment for Breaking Dormancy (Physiological Dormancy)
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
Potassium Nitrate ( KNo3)
- The germination substratum may be maintained with 0.2% solution of KNo3. It effectively break the seed dormancy.
Gibberellic Acid( GA3)
- This GA3 method is recommended for wheat, oat etc.
Sealed Polythene Envelops
- When a high proportion of fresh un-germinated seeds are found at the end of the standard test, then re-test in a sealed polythene envelop of sufficient size will usually induce these seeds to germinate.
- In case of rice among the several methods for breaking dormancy are available the most suitable method at farmers level is nitric acid treatment.
- Soaking the seed in 0.1 N nitric acid i.e., 6.3 ml per lit. of water for 12 to 24 hours effectively break the seed dormancy, where as the varieties like MTU-1001 which is having 8 weeks and above dormancy duration should be treated with higher nitric acid concentration i.e., 10ml per lit. of water.
- The seed can be utilized for sowing immediately after the treatment or they can be dried thoroughly and can be utilized later for sowing.
Seed Treatment for Protection Against Pests and Diseases
- Several insecticides and fungicides are used in seed treatment to protect the seeds from pests and diseases. These may be merchandized in combination or individual. In case of paddy the seed is treated with carbendism @ 1 gm / Kg of seed to protect against plant diseases.
- The seedling dip in chlorpyriphos 2.5 EC solution @ 1ml /lit of water was suggested to protect against insect pests like rice stem borer, BPH etc.
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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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Seed Storage
Purpose of Seed Storage
- The purpose of seed storage is to maintain the seed in good physical and physiological condition from the time they are harvested until the time they are planted.
Stages of Seed Storage
- The seeds are considered to be in storage from the moment they reach physiological maturity until they germinate or until they are thrown away because they are dead or otherwise worthless.
- The entire storage period can be conveniently divided into following stages.
- Storage on plants ( physiological maturity until harvest).
- Harvest, until processed and stored in a warehouse.
- In - storage ( warehouses)
- In transit ( Railway wagons, trucks, carts, railway sheds etc.).
- In retail stores.
- On the user's farm.
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Seed Production
Systems and procedures
Why Quality Seed Production?
Because:
- Most Important Agricultural Input for a Farmers
- For Increased Grain Yield
- High Product Quality
- Specific requirement
- Business for companies
- Employment to rural people
- Backbone of nation’s economy
Sources Of Seeds
- Nucleus Seed- From Breeder of Hybrid /Variety of Proprietor Breeder
- Breeder Seed - From Breeder of Hybrid /Variety of Proprietor Breeder
- Foundation Seed-From Breeder Seed
- Certified/Truthful Seed- From Foundation Seed.
Nucleus Seed /Breeder Seed à Foundation Seed Stage I/Stage-II –
Certified/Truthful Seed– Commercial grain for farmer’s consumption
Seed Production Planning
MOTTO: Plan every thing before starting
Requirements for Quality seed production facilities
- Good source of BS and F/S- Process start three years in advance before the actual seed production for marketing.
- Trusted Seed Growers.
- Qualified dedicated seed production team.
- Good Seed Processing plant Machinery capable to process the full planned marketing quantity.
- Storage facilities including cold storage provision for off season storage, B/S and F/S.
- Seed Health Laboratory with/without finger printing facilities.
- Grow Out Farm (GOT).
- Reliable, quick and economic transportation facilities.
- Knowledge of statuary Seed laws.
Foundation Seed Production
MOTTO: Purity of Foundation will ensure minimum efforts in field for production of high quality seed
- High purity of breeder seed.
- For in-house hybrids Inspection of Breeder Seed plot by team of other breeders to produce best quality breeder seed.
- For in-house foundation seed of proprietary hybrids involvement of concerned Breeder with F/S production official.
- High Quality foundation seed minimizes the efforts for quality seed production.
- Plan the production of foundation Seed three years in advance before the actual marketing of Seed.
- Inspection of F/S plots by concern Breeders to ensure best quality
Seed Production
MOTTO: Dedicated Team work with Quality consciousness
- Selection of reliable growers before start of season
- Growers should be knowledgeable,financially sound and willing to take extra efforts to take up seed production operations
- Seed production meeting before start of season for allocation of area to different production areas
- Development of new production areas
- Regular field inspections by seed production team at different stages of crop growth to advise growers on different operations
- Random Field inspections by Seed Quality Field Team to monitor the various seed production operations
- Midseason review of seed production to go for alternate area if falling short of targets.
- Group and mass Seed Field inspections by seed production team at critical stages of crop growth in crucial
- highly cross pollinated crops like Pearl millet, maize sunflower and Jowar
- Harvesting and threshing instructions to growers to avoid admixtures.
- Other important operations / instructions as per crop growth
Seed Processing Plant Operations
MOTTO: Quality of processed seed should reflect on Market
- Most important function after seed production
- Overhauling and servicing of plant Machinery before start of season. Replace worn-out parts. Keep spares for emergencies. Extra Important implements to be kept in godown.
- Trained operators of plant machinery
- Separate godown for incoming, processed, sales return and ruminant seed.
- Co-ordination with seed health team for sampling, dispatches and movement of Seed
- Proper up storage and placement of screens,
- Proper records of processed, remnant and processing losses to build full faith of seed grower in company
- Record of seed arrival, dispatch and sales returns
Seed Health Laboratory
MOTTO: To ensure that only and only quality seed reaches the growers .
- All facilities for testing of seed produced
- To ensure that every lot of seed is tested for all the quality parameters of seed health before the dispatch of seed.
- Trained qualified officicial for sampling of seed during processing of seed lots
- Testing of all seed lots for germination, seed vigor, infestations and purity etc
- Confidentiality of seed sampling and testing process
- Seed health laboratory person to be trained in such a way that he catches the problems of seed even visually and to be very careful while testing these suspected lots for seed health.
Grow out tests (GOT)
MOTTO: To Test the Genetic purity of each and every seed lot
- Allocation of area before the season to create all the facility required.
- As no. of lots are known before the arrival of samples hence infra structure should be kept ready before testing season (maximum Kharif)
- Highly technical qualified staff for the Grow out Tests.
- Regular institutional Training of staff to update their knowledge
- All seed lots of hybrids, parental lines and in-house varieties are to be tested through grow out tests.(GOT)
- To strictly adhere to the plant characters of hybrids and varieties/lines
- while taking the plant purity observations.
- In high value crop seeds like sunflower and vegetable hybrids the Finger Printing technology to be used to check the Genetic purity of seed.
- In case of crops where the time gap between seed arrival and dispatch is very less the finger printing has to be adopted to avoid any problem in field.
- Do not look at short term gains while dispatching of seed at the times of Urgency of seed to market.
Handling of Seed complaints
Motto: Find the root cause of problem and rectify it immediately.
- Mechanism to check the authenticity of seed complaints
- Special cell to deal with seed complaints through marketing network.
- To keep records of history of all seed lots to be kept to trace the reasons for complaints.
Find the reason for the complaints
- If the faults found in production/processing/Grow out tests, mechanism to address those problems
Handling of Seed Seed law Enforcement Agencies
Motto: Hassle free marketing of seeds
To Deal with Seed law Enforcement agencies (Agric. Department and Court cases seed failures and consumers forum cases):
- Separate person to deal with court cases
- To keep the records ofall seed lots.
- Knowledge of seed laws to ensure there no convictions.
- Collection of judgments by various courts in country
- Court cases can be handled easily with experience of system.
- Not to accept faults in courts in seed failures but to fight it out
Seed Logistics
Motto: Placement of seed at market in time, safely with least costs in minimum time
- Selection of good reliable transporters through tendering process required for bringing the raw seed from field and dispatch of packed seed in bulk.
- For the small packings dispatches selection of transporters with maximum reach to destinations
- Emphasis on cost reduction through proper planning of dispatches.
- Safe movement of material by sending through quality vehicles with full protection
- Use of railways instead of road transport for bulk transportation and small important seeds to far off locations
- Monitoring of movement of seed till it reaches the destination.
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