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Seed processing, drying, cleaning and upgrading

Seed processing refers to all the steps necessary for preparation of harvested seed for marketing namely handling, drying, shelling, preconditioning, cleaning, size grading testing, and packaging etc.

Layout for seed processing plant

Layout plan for construction of seed processing plant should be carefully planned to ensure that thorough seed cleaning, upgrading, seed treatment and other seed processing operations are carried out efficiently without mixing and damaging seed lots with minimum equipment, personnel, time and at minimum cost.

The following factors should be considered while planning and designing the processing unit:

Need to know Physiological maturity (PM), Harvestable maturity (HM) and harvesting method

·    If these factors are considered, the harvest produce will have the maximum seed quality characters in terms of germination, vigour and storability.

 The maturity is of two types depending on the purpose. If the crop is for grain production it is enough to harvest the crop during harvestable maturity. But when the crop is meant for seed purpose it is advisable to harvest the crop during physiological maturity.

A hybrid is the first generation progeny of a cross between two genetically different identical inbred lines. The individual lines are known as inbreds.  Ineffective cross-pollination is a major constraint in a commercial production of hybrid seeds in many crop species. In such crops manual pollination is the way to produce hybrid seeds. Eg. Cotton. In the case of rice it is highly self-pollinated crop and cross-pollination is a big problem. The increased vigour, uniformity and yield of F1 hybrid have been exploited in most crops where the pollination system allows for convenient and economic cross hybridization.  This system is called breeding tool in exploiting the hybrid vigour.

The term heterosis from Greek means hetero different, osis-condition was coined by skull (1914).

Heterosis or hybrid vigour, refers to the increase or decrease in vigour of off spring (hybrid) over parents. Usually, theses two terms are used synonymous.   But hybrid vigour refers to increased vigour; Heterosis both increased and decreased vigour.

Superiority of the hybrid as hybrid vigour and the mechanism by which this superiority is developed is heterosis (Rangaswamy, 1998).

Seed Production Technology

1.    Paddy
2.    Sorghum
3.    Bajra        
4.    Maize              
5.    Blackgram    
6.    Soyabean                
7.    Cowpea             
8.    Redgram 
9.    Groundnut
10.    Sunflower
11.    Castor       
12.    Gingelly
13.    Tomato
14.    Brinjal
15.    Chilli
16.    Bhendi

The degree of excellence in regard to the physical and genetical characterstics of seeds is called as Seed quality. Seed lots having high genetic purity and high germination percentage and minimum inert, weed and other crop seed and are free from diseases and pest attack, it is said to be a high quality seeds. If it is lacking in any of these qualities, it is said to be low quality seed lots. Only good quality seeds expected to respond well for fertilizers and other inputs used.
 
Viability: It is the ability of embryo to live, grow and develop into a seedling under favorable conditions. The seeds attained maximum viability at physiological maturity stage. Later on seeds start to loss viability.

Multiplication and distribution of high quality seed of improved varieties is a crucial step in agricultural production of any country.

When an entry is identified by the workshop of the concerned project, the breeder begins the seed multiplication of the strain in the following crop season. The seed produced by the breeder after a strain is identified, but before it is released as a variety is termed as the “stock seed”. This seed is known as breeder seed after it is released and notified. In the crop season following notification foundation seed of newly released variety is produced. In the second crop season following the release of variety, certified seed of the variety is produced. Thus the farmer is able to obtain certified seed of a newly released variety for commercial cultivation only in the third crop season following in the notification of the variety. However the seed of such variety reach the farmer even before its release through mini-kit trials. Many other farmers would obtain the seeds from those farmers who conducted the mini kit trials and so on in the next two years. Thus an outstanding variety is likely to reach many farmers even before its certified seeds have been put on sale.

Seed

A true seed is defined as a fertilized mature ovule consisting of embryo, stored material and protective coats. The seed strictly speaking is an embryo a living organism embedded in the supporting or the food storage tissue.

A seed stands for any of the following used for sowing or planting.

1.    Seeds of food crops including edible oil seeds and seeds of fruit and vegetables.
2.    Cotton seeds
3.    Seeds of cattle fodder
4.    Jute seeds
5.    Seedlings, tubers, bulbs, rhizomes, roots, cuttings, all type of grafts and other vegetative propagated material for food crops or cattle fodder.

Seed technology is defined as “that discipline of study having to do with seed production, maintenance quality and preservation (Cowan, 1973).

Feistritzer (1975) has defined seed technology as the method through which the genetic and physical characteristic of seeds could be improved. It involves such activities as variety development, evaluation and release, seed production, seed processing, seed storage, seed testing, seed certification, seed quality control and seed marketing etc.

So seed technology in widest sense, includes development of superior crop plant varieties, their evaluation and release, seed production, seed processing, seed storage, seed testing, seed certification, seed quality control, seed marketing, seed distribution and the related research on these aspects,

The major goal of seed technology is to increase agricultural production through the spread of good quality seeds of high yielding varieties. To achieve this goal, the quality seeds must be rapidly multiplied and supplied to the farmers at proper time with the reasonable price.

Seed Sampling

The size and quantity of seed sample required for seed quality testing remains small as compared to the seed lot hence, representative samples are randomly drawn for this purpose. The process of obtaining a uniform and representative sample from a seed lot for seed quality testing is called seed sampling. The samples are prepared in accordance to ISTA rules to ensure that small size sample should represent truly and in the same proportion all constituents of seed lot.

Mini seed testing lab analytical register

Seed storage is the preservation of viable seeds from the time of collection to the required for sowing. It is important to get adequate plant stands in addition to healthy and vigourous plants.

Objectives

i. To maintain initial seed quality during storage period by providing suitable conditions.

ii. To maintain the seed germination and emergence rates.

iii. To prevent the seed deterioration during storage period.

iv. To maintain the physical and physiological seed qualities.

The seed moisture content is the amount of water present in the seed. It is generally expressed in percentage of dry and wet seed weight. It is the loss in weight of the original sample when it is dried. High moisture content in seed sample favors the mechanical damage, seed longevity, incidence of disease and insect pests.

Objective

i. To know the moisture content of seeds by suitable methods
ii. To suggest the seed drying.

Seed Viability Test

Germination test for a seed lot is a pre-requisite to know its potential of emergence under field condition. However, this test requires few days to weeks and a month in some cases. Tetrazolium test gives quick information on seed viability or germinability. It makes possible to distinguish red coloured living parts of seeds from the colourless dead ones. Staining of seeds determines  viability.  Completely  stained  seeds  are  viable  while,  partially and comparatively unstained seeds are non-viable. This test is not valid as compared to seed germination test.

Seed Germination Test

Germination is the process of emergence and development of seed embryo into a plant under favourable environmental conditions of water, soil, sunlight and temperature. The best example of germination is the sprouting of a seedling from a seed of an angiosperm plant. It reflects the ability of seed to produce a normal plant under favourable environmental conditions. The germination rate of a particular seed lot is a key indicator of its performance in the field.

Physical purity test determines the proportion of pure seed, other crop seed, weed seed, inert matter, moisture and germination components in the seed lot by weight in percentage in accordance to prescribed Seed Standards. It thus, helps in improving the plant stand, raising a pure crop by eliminating other crop seeds, weed seeds and disease free-seeds. Seed must not be sold until the percentage of pure seed, other crop seed, weed seed, and inert matter are in accordance to seed physical purity standards. Physical purity test is required for seed certification or seed law enforcement and it is a pre-requisite for ger- mination test.

1. Isolation distance

Seed
The seed, in botany is a mature ovule, consisting of an embryo together with a store of food all surrounded by a protective coat and bear ability to develop a new plant on optimum conditions of soil, moisture and light. It usually develops after the fertilization on an egg cell by male generative cell from a pollen grain. Seeds of some species develop without the intervention of the male cell, formed entirely of ‘mother’ tissue. Such seeds are called apogamic seeds. In seed technology, the seed is seed or any vegetatively propagated material produced from seed crop in accordance to Indian seed standards and has potential to develop new crop in presence of soil, moisture and light.

Notified Varieties of Different Seed Spices

India is famous as the ‘Land of Spices’ world over. Spices are nature’s gift to humankind for flavoring our food. They are also used as preservative and in pharmaceuticals. India is the largest producer, consumer and exporter of seed spices and their value added products. About 63 different spice crops are cultivated in the country. Among them, seed spices are annual herbs, whose dried seeds or fruits are used as spices. These crops share 21.87% in terms of quantity and 7.42 % in terms of value to total spices export in the country. The country grows a wide variety of seed spices like coriander, cumin, fenugreek and fennel as major crop, while, dill, nigella, ajwain, anise, celery, caraway, parsley, black cumin and few other are categories as the minor seed spices.

Storage of paddy seed lots after harvesting is one of the crucial aspects of processing shopfloor. Paddy due to increased mechanised harvesting may loose vital seed quality parameters. Since seed growers cannot buy a combined harvester themselves-they resort to hiring of this machine. Sometimes in the hurry of completing harvesting they harvest the crop at un-safe moisture content. This un-safe moisture content may go up to 50-60% also. Harvesting of seed crop with high moisture has adverse effect on storability. Ensuring safe seed moisture is very critical especially during rabi-summer seed production cycle. Most of the growers depend on sun drying for reducing the seed moisture. But paddy should not be dried >3% in one cycle. Follow tempering and convection cooling after every cycle and repeat the cycle till seed attains safe moisture content (14%).