A seed is a developed, fertilized ovule from a flowering plant that contains an embryo or rudimentary plant. Seed vigour is ‘the sum total of those properties of the seed that determine the potential level of activity and performance of the seed during germination and seedling emergence’ (Perry, 1978, 1980).It is a concept associated with aspects of seed performance such as rate and uniformity of seed germination and seedling growth, emergence ability of seeds under unfavorable environmental conditions, and performance after storage, particularly the ability to germinate, rather than a single measurable property. AS a result, vigour can be defined as the potential performance of viable seeds in agricultural practice, which is governed by the complex interaction of genetic and environmental factors (Whittington, 1973; Hodgkin and Hegarty, 1978). The causes for this diversity in performance, however, are complicated and little understood.
Important seed vigour traits for predictable crop establishment
A seed’s vigour determines how well it performs, its ability to yield strong seedlings that become robust and uniform plants. On the other hand, seeds seen to be low in vigour will produce weaker seedlings that will be more susceptible to attack, contamination, and other environmental issues.
• Size matters: Seeds should be uniform in size; this is an indication that they’re all of the same quality and purity. A mixture of sizes could be a sign that the seeds haven’t been graded properly, meaning it’s more likely there will be contaminants and weaker specimens among them.
• Paddock Competition: The more evenly the seed distribution in the paddock the less chance that weeds will compete for vital nutrients and moisture
• Seed purity: As well as being uniform in size, seeds should also contain only a single variety. Any mixture among the seeds can introduce cross fertilisation potential or enable weaker seeds to pass on contaminants to the stronger seeds, ruining your crop.
• Seed cleanliness: Seeds are cleaned to remove the chaff and any inert material that can damage their performance. Dirt, twigs, straw, stones and weeds carry contaminants that can limit the seed’s productivity and possibly render it useless.
• Germination power: Seeds that are of uniform size, shape, colour, purity and cleanliness will produce stronger seedlings that become healthy plants. Seedlings from robust seed stock will germinate faster giving early, uniform stands that shield and protect each other.
Vigor testing not only determines the percentage of viable seed in a sample, but it also represents the seeds potential to generate normal seedlings under optimum or adverse growing condition similar to those which may occur in the field.
A germination test, which gives the growing seedlings with optimal temperature, moisture, and li ght conditions, can classify seeds as viable. They may, however, be unable to continue growing and complete their life cycle under a variety of outdoor circumstances. Vigor testing is an important procedure in seed production operations because seeds lose vigor before they lose their capacity to germinate. For carryover seeds, vigor testing is very crucial, especially if the seeds were stored under unknown or unfavorable conditions. Seed vigor testing is also used to determine a seed lot’s storage potential and to rate distinct seed lots with varied attributes.
Method of measuring seed vigor
Cold test, accelerated aging test, electric conductivity test, seedling vigor classification, and seedling growth rate are among the tests that are used to measure seed vigor.
Seedlings have four significant morphological sites for evaluating vigor:
• Root system.
• Hypocotyl (the embryonic axis between cotyledons and root).
• Cotyledons (storage tissue of reserve food for seedling development).
• Epicotyl (the embryonic axis above the cotyledons).
In this test, seedlings are classified as ‘strong’ if the above four areas are well developed and free from defects, which is indication of satisfactory performance over a wide range of field conditions. On the other hand, normal seedlings with some deficiencies such as missing part of the root, one cotyledon missing, hypocotyl with breaks, lesions, necrosis, twisting, or curling are classified as ‘weak’.
Seed vigour is a complicated feature that is determined at many phases of the mother plants and seed’s development, as well as by the surrounding environment. Furthermore, its actions are dependent on the current environment and act from seed imbibition until seedling emergence. Seed vigour is a critical issue for agriculture and the seed industry. It demands well-established plants that germinate fast and uniformly, producing large amounts of nutritious product. The stronger the seed, the more likely you are to succeed, yet it is still poorly understood and understudied in academic study. With an ever-increasing population and rapid climate change, seed vigour is becoming increasingly important. Thus, seed vigour is important to unfold the potential yield performance of the crop.