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 dividends sought to be obtained by introduction of new superior crop plant varieties. In other words, seed production must be carried out under standardized and well-organized condition.
Natural crossing occurs due to following three reasons
Natural crossing occurs due to following factors
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 .
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.
Maintenance of Genetic Purity During seed Production:
The various steps suggested), to maintain varietal purity, are as follows.
The various steps suggested for maintaining genetic purity are as follows:
A crop variety to be grown for seed production in an area must be adapted to the photoperiod and temperature conditions prevailing in that area.
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.
The seed crop must be isolated from other nearby fields of the same crops and the other contaminating crops as per requirement of the certification standards.
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.
The variety of seed production must be carefully selected, should possess disease resistance, earliness, grain quality, a higher yielder, and adapted to the agroclimatic conditions of the region.
Depending upon the requirement the following seed treatment may be given
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.
Lower seed rates than usual for raising commercial crop are desirable because they facilitate rouging operations and inspection of seed crops.
The most efficient and ideal method of sowing is by mechanical drilling.
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.
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:
14. Disease and insect control: Successful disease and insect control is another important factor in raising healthy seed crops. Apart from reduction of yield, the quality of seeds from diseased and insect damaged plants is invariably poor.
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 fertilizers.
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.
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 order to preserve seed viability and vigour it is necessary to dry seeds to safe moisture content levels.