A novel picture of seed priming, enhancement, coating and pelleting of vegetable seeds
Authors: Neha Yadav* and Aniket Vilas Chandanshive#
*Division of Vegetable Science, ICAR-Indian Institute of Horticulture Research, Hessaraghatta Lake post, Bengaluru
#Division of Vegetable Science, ICAR-Indian Agriculture Research Institute, Pusa Campus, New Delhi 110012
E-mail: nehayadav67.ny@gmail.com

Seed can be treated in several ways prior to planting to get the better quality and yield potential of the resulting product. In agricultural inputs, seed is the most significant entity for following reasons viz., it is a propagule that carrying unique genetics, which culminate in optimum crop response to varying environments. It is the reproductive unit responsible for ensuring successful establishment for most agricultural especially vegetable crops. There are many factors that can narrow down the gap between potential and farm level yield. Among them, use of quality seed is the most important as quality seeds ensure better germination as well as better yield. Poor seed handling condition gives rise to deterioration of seed quality and the resultant loss of viability, greatly affects seed vigor, as a result the quality of the seed becomes bad and the seed is unusable for crop production. Hence, some physical and chemical operations are performed with the seeds between the processing to storage time to overcome these problems.

Seed is defined as a miniature plant or in detail it is a fertilized, mature ovule consists of an embryonic plant together with a store of food surrounded by a protective coat. A typical seed includes three basic parts, viz., an embryo, a supply of nutrients for the embryo and seed coat, respectively. In ancient period evidences found that the today’s practices related to seed that are identical in principle to current priming techniques, evidences was found in Vedas, Bible and Theophrastus (372-287 B.C.) that the seeds of the cucumber are pre-soaked seeds in milk or water to make faster germinate. Simultaneously, the coated and pelleted seeds are also traced in Egyptian pyramids and Greek farmers used the technique of density separation in water. The practice of coating the seed was practiced 2000 years ago. The ancient Chinese people coated rice seeds in mud balls in order to fasten the seeds germination in flooded paddy field, which eliminated the problem of seed drifting.

Seed priming

Seed priming is broadly defined as it is a pre-sowing seed treatment in which seeds are soaked in an osmotic solution that allows them to imbibe water, which go through the first stages of germination but does not permit the radicle protrusion through the seed coat, respectively. It is used to increase speed of the germination rate, consistency and overcome its seed dormancy. In priming, seeds are hydrated in a controlled manner to provide enough water to initiate the metabolic processes of germination, but not enough to allow germination to be completed. Seed priming is a practice of regulating the process of germination by supervising moisture content in seed and temperature in this process initial biochemical stages required for the process of seed germination is undertaken, which brings the seed closer to the point of germination. These processes involve advancing the seed to an equal stage of the germination to facilitate quick and uniform emergence. So priming of seeds is an important practice in order to secure the benefits of seed priming.

Generally seeds are primed for the various reasons such as to overcome or alleviate phytochrome induced dormancy in plants leafy vegetables. To decrease time required for germination and emergence of the seeds. To improve the uniform stand of the crop, aiding in production management and increasing the chance for uniformity at harvest. To extend the temperature range, which required to seed can increase the rate of germination at any temperature range. It can reduce germination time at field condition. These are the vegetables in which the priming is done viz., okra, onion, water melon, chilli, sponge gourd and ridge gourd etc.

Methods of seed priming

  1. Hydropriming It is a technique in which the sedds initiated for germination without emergence of the radical. The process involves soaking of the seeds in water or in priming solution followed by drying prior to sowing seeds. Hydropriming enhances the germination and growth of the seedlings earler, which determine a good stand of the crop, better establishment and consequently a better yield. In addition, it it reduces the infection of the seeds.
  2. Osmopriming It is a sustainable method in which seed is soaked in a solution of polyethylene glycol to increased germination, better crop establishment, uniform emergence, growth of roots and good plant performance at field condition.
  3. Halo priming It is a type of seed treatment in which seeds are treated with salt in order to improve germination and decrease salinity intolerance. That improves seed germination and vigour. It is a technique which involves uptake of water by the seed followed by drying to initiate the early events of germination. The benefits include rapid, uniform and increased germination, improved seedling vigour and growth under a broad range of environments resulting in better stand establishment. It is cost effective, economic, non-toxic and eco-friendly as easily adaptable by the small and marginal farmers. It also extends shelf life of the seed in storage and ensures consistent performance over a wide range of environmental conditions.
  4. Matrix priming It is based on physiological processes in which it improves the germination characteristics of seeds accomplished by partially hydrating maintain specified moisture temperature and aeration. It improves establishment of small-seeded vegetable crops by increasing germination rapidity and synchrony of seeds and productivity.
  5. Nano priming In this technique the nano- microscopic particles less than 100 nm of the particle are used for priming with purpose to increase germination percentage, seedling growth and seedling vigour. It enhances the germination percentage as well as seedling dry weight and vigour in most of the crops.
  6. Bio-priming It is the best sustainable and ecological technique to avoid the use of chemicals. In this method various bio-control agents are used as a layer over the seed surface as a protective coat, which is safe for environment and human health too. Generally, Trichoderma viridae and Trichoderma harzianum are common fungal antagonists are used in bio-priming.
Advantages of seed priming

1. It improves rate of germination

2. It improves seedling establishment in field

3. It imparts faster growth rate in seedling

4. It imparts drought tolerant in to the seedlings

5. It eliminate or greatly reduce the amount of seed-borne fungi and bacteria

6. The crops can compete more effectively with weeds.

7. It Increases the overall yield potential of the crop.

8. It enables seed to germinate even under adverse agro-climatic conditions.

9. It improves uniformity to optimize harvesting efficiency.

10. It Increases vigour for fast and strong plant development.

Seed Enhancement

Seed quality enhancement is the post harvest treatment that improves germination or seedling growth, which facilitates the delivery of seeds and other materials required at the time of sowing. Technically, it is described as the range of realistic beneficial management techniques, which performed on seeds after harvesting and conditioning to improve their physical or physiological performance of the seed. seed enhancements is basically done to improve hygiene and mechanical properties of the seed, breaking of dormancy subsequently, synchronized germination, equal distribution of the nutrients and impart stress tolerance. It also upgrades the quality of seeds by eliminating immature and damaged seeds. The process also eliminates the non-viable and low vigour seeds by exploiting differences in seeds dimensions like volume, size and density, weight, colour sorting, polishing and scarification, respectively. Various hydration techniques such as priming or applying active plant growth regulators to control the hydration level with in the seeds so that the metabolic activity of the seed necessarily required for germination could occur by preventing but radicle emergence. Commercially there are several different techniques of priming are used such as Osmo-Conditioning or Osmotic priming in which Polyethylene glycol, KNO3 and NaCl are used, Matri-Conditioning or Solid-Matrix conditioning in which sand, Peat Moss and Vermiculite etc., are used.

Enhancement of the seed or seed enhancement refers to a mixture of technologies, which are used to augment the steadiness and performance of the seed, to improv yield and quality of the seeds or produce. Now a days this seed enhancement technology gaining popularity because of its increasing potential to better resistance to seed born disease diseases, it improves vigor of the seed and modify the ability to seed emergence. The term seed enhancement is used frequently in recent times in commercial seed production and in the scientific community to describe beneficial techniques performed on seeds after harvest but prior to sowing. The term seed enhancement generally deals with post harvest management that improves germination drastically and improves growth of the seedlings that smoothly progress the delivery of seeds and material required at the time of sowing. These are basically a value added techniques, which are performed on seed lot. It includes three general methods viz., pre sowing hydration seed treatments, coating technologies and seed conditioning. Seed enhancement is not new to agriculture, and earlier practices have been described for priming, coating and pelleting. Seed enhancement includes three general methods pre-sowing hydration seed treatments, coating technologies and seed conditioning. The seed of the vegetables like, tomato, sugar beet, melon, Chinese cabbage, chilli and carrot etc are enhanced.

Advantages of seed enhancement

  1. It gives higher yield.
  2. It improves crop quality drastically.
  3. It makes crop safeguard against disease.
  4. It protects crop against pest and disease
  5. It makes crop earlier establishment and early harvest.
  6. It manages weed more precisely providing a quick and uniform initiation.
Seed coating

Seed coating refers to the application of coating substances or material to the seed surface, which enhances the seed placement and performance without altering shape on the seed coat which regulate and improve germination. Seed coating includes any process for the addition of materials to the seed. It is also known as seed that has been pelleted, tableted or taped. Seed Coating comprises of film coating, coloring and pelleting of the seed.

Now days a film coating active ingredient is applied in a quick-drying polymer film around the seed is used and is gaining popularity among the farmers. Precise amount of active ingredients along with a liquid material directly applied on to the seed surface without obscuring its shape. A major advantage of film coating is reduced loss of active material from the seed during seed transport and handling. Seed pelleting technologies are used to alter seed shape, surface properties, density and size to enable more precise seed placement in the planting tray or soil. It eliminates clustering of seed that leaves too much or too little space between plants within a row. Seed pelleting is also used to deliver a range of beneficial additives, including micronutrients and plant protection agents. The vegetables like lettuce tomato, cabbage, broccoli, cauliflower, carrot, radish, onion are coated.

Advantages of seed Coating

  1. It protect against fungal attack, insect predation.
  2. It is useful for uniform growth and establishment of the crop.
  3. It enhances the seed germination process.
  4. It gives protection against soil borne diseases insects and insects.
  5. It helps plant to withstand even in the adverse conditions.
  6. Increased visibility of seed in the soil and flow ability in the planter during sowing. Seed Pelleting The term pelleted seeds refers to the addition of inert filler materials to increase the apparent seed size and weight. The process of enclosing the seed with small quantity of ingredients along with filler materials to produce a globular unit of uniform size to facilitate precision planting. Seed pelleting may obscure the original shape and size of the seed. The pelleting material must be robust enough to remain in place during handling, transport and sowing. Pelleting guarantees that the active ingredients are distributed evenly among individual seeds within a seed lot. The covering layer is designed to break open after sowing, so that it doesn’t hinder seed germination. The seeds of onion, tomato and lettuce were used. Advantages of seed pelleting
  1. It reduces seed rate required for planting.
  2. It increase in size of the seed .
  3. It makes sowing and planting precision.
  4. It maintains the seed moist by making moisture available from soil.
  5. It efficiently supply the available growth regulators and nutrients.
  6. It stimulates the seed germination.
  7. It influence of micro-environment required for better germination and seedling emergence.
  8. It saves the cost of chemicals and fertilizers applied to soil.
  9. It supply of oxygen abundantly.
  10. It makes crop and seedling establishment uniformly.
  11. It increase overall yield of the crop.
  12. It is best method to problematic soil.
The productions and timely supply of quality seeds to the farmers are most crucial and challenges the technology. Seeds are considered as basic input and output in agriculture. Whereas, the production and timely supply of quality seeds to the farmers are most crucial and challenge. Quality seed is the potential tool for highest earning to farmer of all other inputs. Without good seed, the investment on fertilizers, water, pesticides and other inputs will not pay the desired dividends. Therefore, production of quality seed and maintenance of high germination is of utmost significance in the seed program. In this way, seed enhancements technology has a core objective plays a significant role in improvising the seed performance. In conclusion many of our so called modern seed enhancements have a historical basis dating back to hundreds to thousands of years ago.

About Author / Additional Info: