Major Seed Quality and Its Characters

Concept

Seed quality is the possession of seed with required genetic and physical purity that is accompanied with physiological soundness and health status. The quality of seeds is considered as an important factor for increasing yield. The use of quality seeds helps greatly in higher production per unit area to attain food security of a country . Quality seeds have planning, congenial regulatory system, facilities for capacity and structural improvement both in public and private sector are required for production, processing, preservation, and distribution of sufficient quantity of quality seeds in time to farmers.

Seed

Seed is a basic input in agriculture. Strictly speaking seed is an embryo, a living organism embedded in the supporting or the food storage tissue. In seed, the importance is given to the biological existence whereas; in grain the importance is given to the supporting tissue the economic produce. seed is the most vital and crucial input for crop production, one of the ways to increase the productivity without adding appreciably to the extent of land now under cultivation by planting quality seed.

Quality Seed

Quality seed is defined as varietally pure with a high germination percentage, free from disease and disease organisms, and with a proper moisture content and weight. Quality seed insures good germination, rapid emergence, and vigorous growth. These aspects translate to a good stand (whether greenhouse or field). Poor quality seed results in “skips,” excessive thinning, or yield reductions due to overcrowding, all of which diminish profitability.

Importance of quality seed

• Seed is a vital input in crop production;
• It is the cheapest input in crop production and key to agriculture progress.
• Crop status largely depends on the seed materials used for sowing
• Response of other inputs in crop production depends on seed material used
• Ensures genetic and physical purity of the crops
• Gives desired plant population
• Capacity to withstand the adverse conditions
• Seedlings produced will be more vigourous, fast growing and can resist pest and disease incidence to certain extent
• Ensures uniform growth and maturity
• Development of root system will be more efficient that aids absorption of nutrients efficiently and result in higher yield.
• It will respond well to added fertilizer and other inputs.
• Good quality seeds of improved varieties ensures higher yield atleast 10 – 12 %

Major seed quality character

I. Physical attributes of seed quality

Physical seed quality refers to the percentage of pure seed of the right crop in a seed lot; sometimes seed size is also accounted for. It is measures by some components viz. Analytical purity, moisture content, size, appearance, colour, insect bites, and presence of other undesirable materials.

A. Analytical purity

Analytical purity also called physical purity, indicates how much of the sample consist of seed of the species being tested and how much contamination of in the form of other seed and inert matter is present (Wingell, 1983).
It is essential to have specific information on purity about the seed lot such as:

Pure Seed: The pure seed shall refer to the species stated by the sender, or found to predominant in the test, and shall include all botanical varieties and cultivars of that species.

Other Seed: Other seeds shall include seeds and seed like structures of any plant species other than of pure seed.

Species purity: When it is desirable to avoid contamination of one crop species by another similar type, a larger sample is examined and the number of seeds of the species is counted. The result is then expressed as the number of seeds in the weight of seed examined, e.g. two per kg. (Thomson, 1979).

Obnoxious weed: There are some species of weeds which are not universally present on all farm and which one established are difficult to eradicate. Weeds of this kind are described as obnoxious weed. Certified seed should be free from them. It is expressed by number in the weight of seed examined. (Thomson, 1979 and ISTA, 1985).

Inert Matter: Pieces of broken or damaged seed one half of the original size or less, straw, chaffs, stone, dust, nematode, gall, dead or living units, ergots etc. i.e. materials which have no life and which are not considered as seed of any plants are separated as inert matter (Thomson, 1979 and ISTA, 1985). And percent by weight is calculated.

II. Genetic purity

It is the true to type nature of the seed. i.e., the seedling / plant / tree from the seed should resemble its mother in all aspects. This quality character is important for achieving the desired goal of raising the crop either yield or for resistance or for desired quality factors.

III. Physiological Quality

Physiological quality refers to the ability of a seed to germinate and includes components like germination capacity, viability, vigour and characteristics related to dormancy.

1. Germination capacity: Germination in a laboratory test is the emergence and development from the seed embryo of those essential structures which for kind of seed being tested, indicate the ability to develop into a normal plant, under favourable condition in soil (ISTA, 1985). The germination capacity of a lot is the percentage by number of pure seeds, which produce seedlings in a laboratory test (Thomson, 1979).

The first thing in crop cultivation is that seed must germinate. A seed without viability is no seed and in no way can be used for crop production. Germination of seed should be as such which can ensure establishment of optimum plant stand for desirable production.

2. Viability: Viability means that a seed is capable of germinating and producing a “normal” seedling. Therefore, it is used synonymously with germinating capacity. In this sense, a given seed is either viable or non-viable, depending on its ability to germinate and produce a normal seedling; thus, only seed lots representing populations of seeds may exhibit levels of viability. In another sense viability denotes the degree to which a seed is alive, metabolically active, and possesses enzymes capable of catalyzing metabolic reactions needed for germination and seedling growth. However, a quality seed must have viability.

3. Vigor: Vigor has been defined as that condition of active good health and natural robustness in seed which upon planting, permits germination to proceed rapidly under a wide range of growing conditions. It has also been defined as the potential for rapid uniform germination and fast seedling growth under general field conditions.

IV. Seed Health

Health status of seed is nothing but the absence of insect infestation and fungal infection, in or on the seed. Seed should not be infected with fungi or infested with insect pests as these will reduce the physiological quality of the seed and also the physical quality of the seed in long term storage. The health status of seed also includes the deterioration status of seed which also expressed through low vigour status of seed. The health status of seed influences the seed quality characters directly and warrants their soundness in seed for the production of elite seedlings at nursery / field.

Characteristics of good quality seed

Higher genetically purity:

Higher physical purity for certification

Possession of good shape, size, colour, etc., according to specifications of variety

Higher physical soundness and weight

Higher germination ( 90 to 35 % depending on the crop)

Higher physiological vigour and stamina

Higher storage capacity

Free from other crop seeds ( Expressed in number /kg) – Other crop seeds are the plants of cultivated crops found in the seed field and whose seed are so similar to crop seed that is difficult to separate them economically by mechanical means. Eg. Mixtures of Wheat, oats seeds in barley.

It should be free from objectionable weed seeds -These are plants of weed species which are harmful in one or more of the following ways.

The size and shape of their seeds are so similar to that of the crop seed that is difficult to remove their seed economically by mechanical means.

Their growth habit is detrimental to the growing seed crop due to competing effect.

Their plant parts are poisonous or injurious to human and animal beings

They serve as alternate hosts for crop pests and diseases.

Reference :

Abdalla, M. M. F.; D.S. Darwish; A. A. Ali and E.A.A. El-Emam (2000) Investigation on faba bean (Vicia faba. L).15. Variability and clustering of faba bean Land Races . Egypt. J. Plant Breeding 4: 257-272.
Abd El Aziz, A. El-Set and F. H. Shalaby (1999). Physiological studies on response of new released faba bean varieties to different plant populations. Zagazig J. Agric. Res 26 (5) : 1229-1244.
Abo El-Zahab, A.A.; A.A. Al-Babawy and K.Abd El-Latif (1981). Density studies on faba bean (Vicia faba L). I. Seed yield and its components. J. Agron. & Crop Sci. 150 : 291-302.
Abo-Shetaia, A.M.A. (1990). Yield and yield components response of faba bean (Vicia faba L.) to plant density and NP fertilization. Ann. Agric. Sci., Fac. of Agric.; Ain Shams Univ., Egypt, 35 (1): 187-204. Abou – Salama, A.M. and R.A. Dawood (1994). Yield re

Writer: Anish Gyawali