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International Journal of Advance Research, Ideas and Innovations in Technology
© 2021, www.IJARIIT.com All Rights Reserved Page| 675
ISSN: 2454-132X
Impact Factor: 6.078
(Volume 7, Issue 4 - V7I4-1347)
Available online at: https://www.ijariit.com
Seed Vigor Testing in Cotton: A Review
Dr. Vaibhav V. Ujjainkar
vvujjainkar@gmail.com
Dr. Panjabrao Deshmukh Krishi Vidyapeeth,
Akola, Maharashtra
Dr. Manoj W. Marawar
mwmarawar@gmail.com
Dr. Panjabrao Deshmukh Krishi Vidyapeeth,
Akola, Maharashtra
ABSTRACT
Attaining seed and seedling vigor in cotton is the important objective of researchers and producers. Seed vigor can be defined
in terms of low degree of seed deterioration. Seed is a connecting link between two generations of plants or crops, hence it is a
carrier of new technology or new improvements made by the breeders. Seed vigour is the important quality, needs to be
assessed primarily to supplement germination and viability tests to gain insight into the performance of a cotton in the field or
in storage. Seeds are prime factor for yield, nutrition, and overall the food security. The key component of the performance of
crop seeds is the complex trait of seed vigour. In agriculture, the crop yield and resource use efficiency depend on successful
plant establishment in the field, and it is the vigour of seeds that defines their ability to germinate and establish seedlings
rapidly, uniformly, and robustly across diverse environmental conditions prevailing in region. Improving the vigour of sowing
material viz., seed to enhance the critical and yield-defining stage of crop establishment remains a primary objective of the
cotton seed industry. The knowledge of the regulation of seed germination has developed greatly in recent decades. Here we
consider seed vigour at an eco-physiological, molecular, and biomechanical level. History of seed industry has witnessed the
incremental improvements, but further actively focused efforts are needed to produce vigorous and quality cotton seeds. In this
paper, the focus is to discuss the ways by which the basic plant science could be applied to improve the seed performance in
cotton production.
Keywords: Cotton, Seed Germination, Seed Testing and Seed Vigour
1. INTRODUCTION
Cotton (Gossypium spp.) is the natural textile fibre crop and a significant contribution in oilseed production globally. Cotton
fabric is the most skin friendly of all natural fibres available on earth. Cotton contributes to 35.0% of the global fabric needs and
60.0% of clothing in India. It is estimated that in India more than 10.0 million farmers cultivate cotton and about 30 million
persons are employed in cotton value addition (Anonymous, 2015)
Cotton is cultivated nearly in eighty countries, while India remains the leading country in terms of area under cotton cultivation
and raw cotton production in the world. As per Committee on Cotton Production and Consumption (COCPC) estimate, cotton
production in India during 2020-21 is expected to produce 371 lakh bales of 170 kg from 129.57 lakh hectares with a productivity
of 487 kg lint/ha. During the current year 2020-21, Gujarat, Maharashtra and Telangana were the major cotton growing states
covering around 68% (88.3 lakh hectare) in area under cotton cultivation and 63% (236 lakh bales) of cotton production in India.
(Anonymous, 2021).
The evolution of vigor testing in agricultural seeds has been a slow, arduous, and still unfinished process (McDonald, 1993). A
widely accepted definition of 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). In 1977, the International Seed
Testing Association (ISTA) defined seed vigor as, (in part), "the sum of those properties which determine the potential level of
activity and performance of the seed or seed lot during germination and seedling emergence." Recent advances might suggest that
seed vigor is a new idea or concept being positioned for exploitation.
Very early in the history of seed testing, analysts noted differences in the capacity of seed within and among samples for rapid
germination and seedling development and emergence through a physical barrier, i.e., the Hiltner brick-grit test first described in
1911. This capacity was called Triebkraft, meaning "driving force" or "shooting power." Later, the term "germination energy"
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gained ascendency, especially in connection with rate of germination and seedling growth. By 1915, the germination energy
determination - essentially a first count test - and the brick-grit test (cereal seed) were being routinely made in some European
seed laboratories. During the same period and extending through the 1930s, there was much emphasis in the U.S. on use of soil
.tests to aid in interpretation of germination tests and to "calibrate" test results. Globally, the quality of seed is a major concern in
seed industry. The rapid and uniform emergence of vigorous seedlings of the desired cultivar is key factor to ensure the better
plant performance, affecting uniformity of development, yield and quality.
2. RELATION AMONG SEED VIGOR AND GERMINATION:
The basic objective of seed vigor testing is to provide a precise identification of important differences in physiological potential
among commercial seed lots, mostly those having similar germination percentage, aiming to identify lots of higher probability by
performance better in field or in storage.
According to research reported by Delouche and Caldwell, 1960, it is necessary to identify high and low vigor seed lots in a
comparable way to field seedling emergence. Figure 1 highlights the relationship between seed vigor and germination losses
overtime as deterioration progresses. Consequently, a consistent evaluation of seed physiological potential involves both the use
of standardized procedures and the correct interpretation of the meaning and scope of results.
A high quality seed lot (X) that is less deteriorated will show relatively small difference in results from germination and vigor
tests. However, a lower physiological quality seed lot (Y) with higher deterioration level will have higher germination performed
under optimum conditions, but extremely low vigor (Delouche and Caldwell, 1960).
Fig 1: Relationship among seed vigour and seed germination
3. OBJECTIVES OF SEED TESTING
(a) To identify the seed quality problem and its cause
(b) To determine seed quality, thereafter its suitability for planting
(c) To determine the need for seed processing and specific procedures
(d) To determine candidature of the seed as per established quality standards or labeling specifications.
(e) To establish quality and provide a basis for price and consumer discrimination among lots in the market.
(f) The primary aim of the seed testing is to obtain accurate and reproducible results regarding the quality status of the seed
samples submitted to the Seed Testing Laboratories
4. IMPORTANCE OF SEED TESTING
(a) The importance of seed testing focuses on the procedures for assured planting values.
(b) It’s an aid for seed industry to avoid some of the hazards of crop production by furnishing the needed information about
different quality attributes viz., purity, moisture, germination, vigour and health.
(c) Quality control of seed depends on the different seed testing protocols to determine the genuineness of the cultivar.
(d) Testing of seed to evaluate the planting value and the authenticity of the certified lot.
(e) Assessment of the seed quality attributes of the seed lots which have to be offered for sale.
(f) Standard seed testing procedures for the evaluation of the seeds were developed by ISTA. It is obligatory on the part of the
seed analyst to follow rules prescribed by ISTA (ISTA, 1985) in case of International trade.
(g) Economic yield of a crop depends on the quality of seeds which can be evaluated by seed testing (ISTA, 1996).
Seeds, as reproductive units, are expected to produce plants in the field. However, farmers and seed producers have long
recognized that the labeled percent germination often overestimates the actual field emergence of seed lots. This observation is
attributed to the objective of a standard germination test which states that germination is the emergence and development from the
seed embryo of those essential structures which, for the kind of seed in question, are indicative of the ability to produce a normal
plant under favorable conditions. (AOSA, 1991)
5. PHYSIOLOGY OF SEED GERMINATION IN COTTON
In favorable environmental conditions, the four sequential phases of cotton seed germination and seedling emergence occur
during a relatively brief period (within four to six days) in the physiological progression from fertilized ovule to the mature plant,
which produces the next crop of seeds and fiber. When a quiescent, but viable, seed is planted (Baskin et al., 1986; Delouche,
1986; AOSA, 1988; McCarty and Baskin, 1997), the return of the embryo and the sustaining seed storage tissues to active
metabolism is initiated by water imbibitions, the first step in seed germination (Ching, 1972; Bewley and Black, 1978; Pradet,
1982; Simon, 1984; Christiansen and Rowland, 1986). However, in “hard seeds” of some cotton species and varieties, this
chalazal pore is plugged with water-insoluble parenchymatous material (Tran and Cavanaugh, 1984). The presence and
persistence of the plug can produce 'hardseed' or 'seed-coat' dormancy, a form of dormancy in which there is no or minimal water
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uptake (Christiansen and Moore, 1959; Benedict, 1984; Christiansen and Rowland, 1986, Delouche et al., 1995). Seed coat
impermeability can also be induced in cotton when seed water content is reduced to ≤ 10% before planting or germination testing
(Delouche, 1986; Delouche et al., 1995).
6. METHODS OF SEED VIGOUR TESTING
Seed vigour does not reflect a specific property of a seed or seed lot but it is still a concept. Several factors viz., genetic makeup,
growth environment and nutrition source / mother plant, maturity at the time of harvest, seed size and weight, mechanical
stability, deterioration and ageing and pathogens are responsible for difference in seed vigour (Perry, 1980). There is no universal
seed vigour testing method because seed vigour is influenced by multiple factors i.e. species, genotype and environmental
conditions. It can be evaluated by various methods, such as vigour indices, stress tests like accelerated aging test, cold test
(Marcos-Filho, 2015), controlled deterioration test, Brick gravel test etc. The most widely used methods are standard germination
test and accelerated aging test. The seed testing procedures which are described below are based mostly on the international rules
because most of our rules (Chalam et al.. 1967) are based on, ISTA, 1996 and Sharma (2018).
6.1 Growth tests
The basic principle behind these tests is that seeds with high vigour grow at a faster rate as compared to seeds having poor vigour
potential. This difference in growth can be easily observed even under favourable conditions. Vigorous seeds metabolize their
food reserves rapidly, germinate, and establish in the field. Therefore, any method used to determine the quickness of growth of
the seedling will give an indication of seed vigour level.
(a) First count: The test is done along with the regular standard germination test. Number of normal seedlings emerged on the
first count day, as specified for each species are counted. The number of normal seedlings gives an idea of the seed vigour
potential in the seed lots. Higher the number of normal seedlings, greater is the seed vigour.
(b) Speed of germination: This test can be executed using either ‘top of the paper’ or ‘sand’ method of the standard
germination test. One hundred seeds each in four replications are planted for germination. The substratum is kept in a
germinator maintained at recommended temperature for the crop. Number of seedlings emerging daily, are counted from day
of planting till the completion of germination.
(c) Seedling length and dry weight: The seedlings are grown either in laboratory, green house or field. In laboratory, ‘between
paper’ method should be followed. Seeds are planted between two moist towel papers in such a way that the micropyles are
oriented towards bottom to avoid root twisting. The rolled towel papers are kept in the germinator maintained at a
temperature recommended for crop in reference. After a specified period of time (according to reference crop), length of
emerged seedlings is measured and mean seedling length is calculated. Seed lots producing the longer seedlings are
considered more vigorous. For dry weight determination, the seedlings are taken and dried in an air oven at 100°C
temperature for 24 hours.
(d) Seedling vigour indices: These indices are given by Abdul-Baki and Anderson in 1973. These are derived from standard
germination and seedling growth parameters i.e. length and dry weight as per the following formulae:
i)Vigour Index-I = Standard germination (%) × Average seedling length (cm)
ii)Vigour Index-II = Standard germination (%) × Average seedling dry weight (mg or g)
6.2 Stress tests
These tests are based on the assessment of seed performance under stressed conditions. Seeds with higher vigour potential
perform better than low vigour seeds when tested under unfavourable conditions i.e. high or very low temperature, high humidity,
high moisture content, some physical barrier etc.
(a) Hiltner test (Brick gravel test): This test was developed by Hiltner in Germany in 1917. He observed that Fusarium
affected seeds of cereal crops were able to germinate in regular test but were not able to emerge from brick gravels of 2-3
mm size. On the contrary, healthy seeds were able to emerge from the brick gravel. The underlying principle is that the weak
seedlings are not able to generate enough force to overcome the pressure of brick gravels, so this method can be used to
differentiate vigour levels in cereal seeds. The procedure involves the following steps: The sand is seived, moistened and
filled in the germination box leaving about 3 cm empty at the top. One hundred seeds are placed in each box in the
impressions made by a sand marker. After this 2-2.5 cm of porous brick gravel is spread over the seeds. The box is kept in
the germinator at appropriate temperature. After the period required for germination, the seedlings which have emerged
through the brick gravel layer are counted and percentage of emerged seedlings are used to compare seed vigour of different
lots.
(b) Paper Piercing test: The principle of paper piercing test is similar to that of brick gravel test. High vigour seed lots are
expected to produce strong seedlings which can pierce a particular type of paper while seedlings of poor vigour lots may not
be able to pierce the paper.
(c) Cold Test: Cold test was developed in USA to evaluate the seed vigour of maize. In USA, when the corn is planted in late
spring, the soil is humid and cold. The weak seeds do not germinate and establish. Therefore, to simulate the actual field
conditions cold test has been developed. This test aims to differentiate between weak and vigorous seed lots by subjecting
them to low temperature prior to germination at optimum temperature. The procedure involves following steps: After
grinding and properly sieving the soil is filled in tray upto 2 cm depth. Fifty seeds are placed over the sand and covered with
another 2 cm thick layer of soil. The soil is compacted and enough water is added to make the soil saturate its water holding
capacity. After watering, the trays are covered with polythene bags and placed in the refrigerator maintained at 10°C
temperature for one week. After one week, the trays are placed in the germinator at 25°C temperature. The seedlings
emerged after 4 days are counted and germination percentage is calculated by counting the number of normal seedlings.
Higher the germination percentage greater is the vigour.
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(d) Accelerated Ageing (AA) test: The principle of this test is to stress seeds with high temperatures of (40-45°C/130-139°F)
and near 100% relative humidity (RH) for varying lengths of time, depending on the kind of seeds, after which a germination
test is made. High vigor seeds are expected to tolerate high temperatures and humidity and retain their capability to produce
normal seedlings in the germination test
(e) Controlled Deterioration (CD) test: As the name suggests, the test involves the deterioration of samples of seeds from seed
lots in a precise and controlled manner at an elevated moisture content (dependent on the species, often 20%) and
temperature (45°C) for a defined duration.
(f) Seedling Growth Rate Test: This test is closely related to the standard germination test and is useful to figure out field
planting potential under optimal or near ideal conditions. Seeds are planted under optimum conditions and are allowed to
grow for an extended period of time, usually several days past the typical germination period. The seedlings are evaluated by
their growth characteristics, such as stem length, leaf development or root branching.
6.3 Biochemical tests
These are the rapid and accurate methods for estimating the physiological quality of seeds has been studied by seed physiologists
and seed technologists
(a) Tetrazolium (Tz) test: Tetrazolium is a rapid test to estimate seed viability and vigour based on color alterations of seed’s
living tissues in contact with a solution of 2,3,5 triphenyl tetrazolium chloride, thus, reflecting the degree of activity of the
dehydrogenase enzyme system closely related to seed respiration and viability. Dehydrogenase is respiratory enzyme whose
activity proves that cell is alive. The reduction of TTC (colourless) to Formazan (red) is the responsible chemical reaction.
Usually, this test is considered as a viability test but its results can also be interpreted to estimate the vigour of the seed.
Vigorous seeds show dark stains as compared to seeds having poor vigour.
(b) Aleurones TZ test: Aleurone layer of cereal seed plays an important physiological role in germination because it produces
enzymes which hydrolyse the starch reserves of the endosperm. The living Aleurone cells stains red, while dead cells remain
unstained, while the seeds are classified into group according to the area of stained surface
(c) Electrical Conductivity (EC) test: This test measures the integrity of cell membranes, which is correlated with seed vigor.
It is well established that this test is useful for garden beans and peas. It has been also reported that the conductivity test
results are significantly correlated with field emergence for corn, and soybean. As seeds lose vigor, nutrients exude from
their membranes, and so low quality seeds leak electrolytes such as amino acids, organic acids while high quality seeds
contains their nutrients within well structured membranes. Therefore, seeds with higher conductivity measurement are
indication of low quality seeds as vice versa.
7. QUALITY ASSURANCE AND CONTROL
Delouche, J.C. (1982) stated that the physiological and physical qualities of seed can be damaged by drought stress during the
development and maturation period, “Weathering” prior to harvest, mechanical abuse during harvesting and handling operations,
delayed and/or improper aeration and drying, unfavorable storage conditions, and during prolonged storage even under relatively
favorable conditions. Severe “damage” reduces the percentage of germinable seed and can be detected by a germination test. A
germination test made, interpreted, and reported in the "standard" manner does not, however, provide much information on the
extent to which the seeds still capable of germination have been damaged. It does not establish the level of vigor/deterioration of
the germinable seed, which determines how well germination will be maintained until the seed are marketed, and how well the
seed will perform when planted. In a quality assurance and control program, it is important to know the germinative capacity and
performance potential (i.e., vigor) of seed lots after each major operational stage so the rising investment in the seed can be
stopped any time its quality falls below established or acceptable standards, and to identify operational procedures - or
deficiencies therein -which are damaging to quality. Cotton (Gossypium hirsutum L.) plants are vulnerable to various stresses
during the seed and seedling stages. Cathey (1985) provided evidence of the importance of these growth stages by finding a
significant, positive correlation between yield and heat unit accumulation only during the seedling stage
It is equally or even more important in a quality assurance and control program to obtain information from which projections can
be made about the quality of the seed in the future - the next marketing, distribution and planting season. A combination of the
germination test, vigor tests and other special tests such as mechanical damage and seed health analyses can provide the
information needed to monitor and control seed quality during the operational stages from production to storage, and to assure that
lots of seed marketed are in good physiological condition.
8. CONCLUSION
The progress of ovule to seed and seed to plant ratios remains the ultimate aim of all research workers and developmental efforts
of field of seed science and technology. The seed scientists have to get acquainted with a lot of different growth events triggering
in seed, which have a great influence on the planting value of seed, and its stability from the harvest period to the sowing season.
Seed vigor testing, should be incorporated the quality assurance and control of seed producing establishments, as a unavoidable
and prime management tool in the cotton seed industry
9. REFERENCES
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