Lect-2 General Prin. of Seed Prod.

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Seed Production Principles Genetic and Agronomic

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General principles of Seed Production and Factors Affecting the Seed Quality Dr. M. K. Karnwal Asstt . Seed Scientist, Genetics & Plant Breeding Deptt . Genetics & Plant Breeding

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General principles of Seed Production Production of genetically pure and otherwise good quality pedigree seed is an exacting task requiring high technical skills and comparatively heavy financial investment. During seed production strict attention must be given to the maintenance of genetic purity and other qualities of seeds in order to exploit the full yield potential of new superior crop plant varieties . In other words, seed production must be carried out under standardized and well-organized condition.

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General principles of Seed Production Basically, there are two seed production principles. (A) Genetic principles (B) Agronomic principles. Genetic Principle – It involves all the factors which may lead deterioration of genetic purity ( true to type ) of a crop variety. In negligence of genetic principles during seed production programme leads deterioration of the varieties .

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(A) Genetic Principle – The important factor & real deterioration of varieties listed by Kadam (1942): Developmental variations Mechanical mixtures Mutations Natural crossing Minor genetic variations Selective influence of diseases The technique of plant breeder General principles of Seed Production

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(A) Genetic Principle – (1) Developmental variation: When the seed crops are grown In difficult environment , Under different soil and fertility conditions, or different climate conditions , or under different photoperiods, or at different elevation for several consecutive generations --- The developmental variation may arise some times as differential growth response. To minimize the opportunity for such shifts to occur in varieties it is advisable to grow them in their areas of adaptation and growing seasons. General principles of Seed Production

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(A) Genetic Principle – (2) Mechanical mixtures: (Varietal mixture) Mechanical mixtures may often take place at the time of sowing, harvesting and at the time of processing grading and packaging. If more than one variety is sown with same seed drill. Through volunteer plants of the same crop in the seed field. or through different varieties grown in adjacent fields. Often the seed produce of all the varieties are kept on same threshing floor. Grading with same grader and packaging the seed in the old gunny bags etc. General principles of Seed Production

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General principles of Seed Production (A) Genetic Principle – (2.) Mechanical mixtures: To avoid this sort mechanical contamination it would be necessary. To rogue the seed fields at least at the three stages. and practice the utmost care during the seed production, harvesting, threshing and further handling of seeds for grading and packaging.

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General principles of Seed Production (A) Genetic Principle – (3.) Mutations: This is not a serious factor of varietal deterioration. In the majority of the cases it is difficult to identify or detect minor mutation. (4) Natural crossing: In sexually propagated crops, natural crossing is another most important source of varietal deterioration due to introgression to genes from unrelated stocks which can only be solved by prevention.

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General principles of Seed Production (A) Genetic Principle – (4) Natural crossing: Natural crossing occurs due to following three reasons: Natural crossing with undesirable types. Natural crossing with diseased plants. Natural crossing with off- type plants.

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General principles of Seed Production (A) Genetic Principle – (4) Natural crossing: Natural crossing occurs due to following factors: The breeding system of species Isolation systems Varietal mass Pollinating agent Size of the pollen grains Duration of pollen viability

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General principles of Seed Production (A) Genetic Principle – (5 ) Minor genetic variations: Minor genetic variations may exist even in the Varieties appearing phenotypically uniform and homogeneous at the time of their release. During later production cycle some of this variation may be lost because of selective elimination by the environment. To overcome these yields trials are suggested

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General principles of Seed Production (A) Genetic Principle – (6 ) Selective influence of diseases: The selective influence of diseases in varietal deterioration is also of considerable importance. New crop varieties often become susceptible to new races of diseases often caused by obligate parasites and are out of seed programmes . Similarly the vegetatively propagated stocks deteriorate fast if infected by viral, fungal and bacterial diseases. During seed production it is, therefore, very important to produce disease free seeds/stocks.

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General principles of Seed Production (A) Genetic Principle – (6 ) Techniques of plant breeders: In certain instances, serious instabilities may occur in varieties due to cytogenetical irregularities not properly assessed in the new varieties prior to their release. Other factors, such as break down in male sterility certain environmental conditions and other heritable variations …..may considerably lower the genetic purity.

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General principles of Seed Production (A) Genetic Principle – Maintenance of Genetic Purity During seed Production: The various steps to maintain varietal purity, are as follows. Avoiding genetic shifts by growing crops in areas in their adaptation only. Use of approved seed only in seed multiplication (Adopting the generation system). Certification of seed crops to maintain genetic purity and quality of seed Inspection and approval of fields prior to planting. Providing adequate isolation to prevent contamination by natural crossing or mechanical mixtures

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General principles of Seed Production (A) Genetic Principle – Maintenance of Genetic Purity During seed Production: 6. Field inspection and approval of growing crops at critical stages for verification of genetic purity, detection of mixtures, weeds, and for freedom from noxious weeds and seed borne diseases etc. Rouging of seed fields prior to the stage at which they could contaminate the seed crop Sampling and sealing of cleaned lots. Growing of samples of potentially approved stocks for comparison with authentic stocks ( Grow out tests ) Periodic testing of varieties for genetic purity

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General principles of Seed Production (B) Agronomic principles- Selection of a Agro-climatic Region Selection of seed plot Isolation of Seed crops Preparation of Land Selection of variety Seed treatment: Time of planting Seed Rate Method of sowing

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General principles of Seed Production (B) Agronomic principles- Depth of sowing Rouging : Supplementary pollination Weed control Disease and insect control Nutrition Irrigation Harvesting of Seed crops Drying of seeds Storage of raw seeds

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General principles of Seed Production (B) Agronomic principles- Selection of a Agro-climatic Region: Growth of the plant and production of good quality seeds are strongly influenced by both genetic and environmental factors. Environmental factors includes : Temperature, rainfall, wind velocity, soil condition and texture, insect activity and their relationship with varietals adaptation in any given locality etc. For good seed crop , a crop variety to be grown for seed production in an area where it must be adapted to the photoperiod and temperature conditions prevailing in that area.

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General principles of Seed Production (B) Agronomic principles- Selection of a Agro-climatic Region: According to the various agro-climatic zones, we can classify the different kind of field crops and vegetable seed production programme to the different seed producing regions Note: Discussed in the Lecture 1

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General principles of Seed Production (B) Agronomic principles- (2) Selection of seed plot: The plot selected for seed crop must be free from - volunteer plants weed plants and have good soil texture and fertility The soil of the seed plot should be comparatively free from soil borne diseases and insects pests etc.

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General principles of Seed Production (B) Agronomic principles- (3) Isolation of Seed crops: The seed crop must be isolated from- Other nearby fields of the same crop. And the other contaminating crop as per requirement of the certification standards.

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General principles of Seed Production (B) Agronomic principles- Preparation of Land: Good land preparation helps in- Improved germination Good stand establishment And destruction of potential weeds. It also aids in water management and good uniform irrigation.

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General principles of Seed Production (B) Agronomic principles- (5) Selection of variety: The variety of seed production must be carefully selected, it should possess- Disease resistance Earliness Grain quality A higher yielder And adapted to the agro-climatic conditions of the region.

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General principles of Seed Production (B) Agronomic principles- (6) Seed treatment: Depending upon the requirement, the following seed treatment may be given- Chemical seed treatment. Bacterial inoculation for the legumes. Seed treatment for breaking dormancy.

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General principles of Seed Production (B) Agronomic principles- (7) Time of planting The seed crops should invariably be sown at their normal planting time. Depending upon the incidence of diseases and pests, some adjustments, could be made, if necessary.

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General principles of Seed Production (B) Agronomic principles- (8) Seed Rate: Lower seed rates than usual for raising commercial crop are desirable because they facilitate rouging operations and inspection of seed crops. (9) Method of sowing: The most efficient and ideal method of sowing is by mechanical drilling. (10) Depth of sowing: Depth of sowing is extremely important in ensuring good plant stand. Small seeds should usually be planted shallow, but large seeds could be planted a little deeper.

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General principles of Seed Production (B) Agronomic principles- (11) Rouging : Adequate and timely rouging is extremely important in seed production. Rouging in most of the field crops may be done at many of the following stages as per needs of the seed crop. Vegetative / pre-flowering stage Flowering stage Maturity stage

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General principles of Seed Production (B) Agronomic principles- (12) Supplementary pollination: Provision of honey bees in hives in close proximity to the seed fields of crops largely cross pollinated by the insects, ensure good seed set thereby greatly increase seed yields. (13) Weed control : Good weed control is the basic requirement in producing good quality seed. Weeds may cause contamination of the seed crop, in addition to reduction in yield:

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General principles of Seed Production (B) Agronomic principles- (14) Disease and insect control: Successful disease and insect control is another important biotic factor in raising healthy seed crops. Apart from reduction of yield, the quality of seeds from diseased and insect damaged plants is invariably poor. (15) Nutrition : In the nutrition of seed crops, nitrogen, phosphorus, potassium, and several other elements play an important role for proper development of plants and seed. It is, therefore, advisable to know and identify the nutritional requirements of seed crops and apply adequate organic fertilizers.

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General principles of Seed Production (B) Agronomic principles- (16) Irrigation : Irrigation can be important at planting for seed crops on dry soils to ensure good uniform germination and adequate crop stands. Excess moisture or prolonged drought adversely affects germination and frequently results in poor crop stands. (17) Harvesting of Seed crops: It is of great importance to harvest a seed crop at the time that will allow both the maximum yield and the best quality seed. In case of orthodox seeds 15-20 percent moisture content should be present at the time of harvest.

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General principles of Seed Production (B) Agronomic principles- (18) Drying of seeds: In order to preserve seed viability and vigor it is necessary to dry seeds to safe moisture content levels. (19) Storage of raw seeds : The best method of sowing seed for short periods is in sacks or bags in ordinary buildings or godown .

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Thank You All !