Concept
of
PHYSICAL PURITY TESTING
Prof. Kumari Rajani
Department of Seed Science & Technology
Bihar Agricultural University
Sabour, Bhagalpur-813210

Physical Purity Analysis
It refers to the analysis for classifying the
composition of a seed lot
It is important for evaluating whether the given
seed sample conforms to the prescribed purity
standards; and whether it can truly represent the
seed lot
The working sample should roughly contain at
least 2500 seeds or of working sample size given
for the species in ISTA Rules
The working sample is separated into four
parts (pure seeds, other crop seeds, weed
seeds, and inert matters) by hand, blowers, or
sieves; and the percentage of each
component is then calculated by weight

1. Pure seed: Seeds of
kind/species stated by sender
or found to be predominant in
the test
2. Other crop seeds: seeds of
other crop species
3. Weed seeds: Seeds of a
common weed/noxious weed
4. Inert matter: all other matters
including soil particles, plant
parts, broken seeds, dust,
chaff, dal etc or which are not
included in pure seed/other
crop seed/ weed seed
Components of Physical Purity Analysis
Physical
Purity
Analysis
Pure
Seed
Weed
Seed
Inert
Matter
Other
Crop
Seed

GRAMINEAE: (Paddy, Wheat, Pearlmillet, Sorghum etc)
Caryopsis, Piece of caryopsis larger than one-half the original size
LEGUMINACEAE: (Gram, Pea, Mung, Urd, Bean, Soybean and
Groundnut etc) and CRUCIFERAE: (Radish, Mustard, Cabbage and
Cauliflower etc)
Piece of seed larger than one-half the original size with testa
Seeds and pieces of seed without testa is regarded as inert matter
Separated cotyledons are regarded as inert matter irrespective of
whether or not the radical plumule axis or more than half of
the testa may be attached
SOLANACEAE: (Chillies, Brinjal, Tomato, Tobacco etc)
Seed with or without testa
Piece of seed larger than one-half the original size with or
without testa
Pure Seed

Purity work board or purity table
Seed divider
Analytical balance
Seed blower
Diaphanoscope using reflected light
Sieves
Sample pan, dishes, forceps, spatula and hand lens
Seed herbarium of crop and weed seeds
Materials Required for Physical Purity Analysis

Diaphanoscope
Purity Work Board
Seed Blowers
Analytical Balance

Aluminum Purity Dishes
Aluminum Purity Spatula
Flexible Arm Illuminator Magnifier
Boerner Type Divider Gamet Type Divider Soil Type Divider
Sample pan

Procedures
Prepare working sample
(Homogenize the submitted sample before reducing
it to the size of working sample )
Separate purity components
(Lighter materials with the help of sieves or blower and
examine each heavier particle individually on the
purity work board )
Weighing of purity components
(Weigh pure seed, other crop seed, weed seed
and inert matter in grams to the desired number of
decimal places)
Calculations and reporting of results
(Calculate the percentage by weight of each
component)

S.N.
Wt. of working Sample
(g)
No of decimal place
required
Example
1. Less than 1 4 0.9025
2. 1 to 9.990 3 9.025
3. 10 to 99.99 2 90.25
4. 100 to 999.99 1 902.5
5. 1000 or more 0 1025
Weighing of each component (pure seed,
other crop seed, weed seed and inert matter) in grams
should be done according to the number of decimal
places shown below:

Add the weight of all the four components
Calculate the percentage by weight of each component to ONE decimal
place only
(based on the weight of all the four components)
The percentage of all component must be total 100
Calculations
S.N. Components
Weight of
Components (g)
Percentage of
component (%)
1. Pure Seed 69.08 98.7
2. Other Crop Seed NIL 0.0
3. Weed Seed 0.66 0.9
4. Inert Matter 0.26 0.4
Total 70 100
Example (Paddy Crop)

 If any component is less than 0.05%, report it as ‘TRACE’
 Component of 0.05% to 0.1% are reported as 0.1%
 If any component is NIL, this must be reported as 0.0%
 The results of purity test be given to one decimal place only
 The Latin names of the crop seed and weed seed should be
reported
The kind of inert matter should be reported
SN Components Paddy
1 Pure seed (Minimum) 98 %
2. Inert matter (Maximum) 2 %
3. Other crop seed (Maximum) 20/kg
4. Weed seed (Maximum) 20/kg
Indian Minimum Seed
Certification
Standards
(IMSCS)
Seed Standards for Certified Class of Paddy
Reporting of Results

 Check the cleanliness of the divider and the containers, work board
and purity dishes
 Pour the entire contents of the submitted sample into the hopper
of the divider
 Mixing of the submitted sample by repeating above steps 2-3 times
to homogenize the submitted sample
 Divide the submitted sample into two half, the sample reduction
should be done till the weight of working sample is obtained
 Put the separated lighter portion on the work board and examine
under magnification for further separating into other crop seed,
weed seed and inert matter, if any present
 Identify the other crop seed, weed seed and record their names. The
kind of inert matter present in the sample should also be identified
and recorded
The following guidelines need to be followed…

Minimum Seed Certification Standard for Pure Seed
Percentage Recommended in Field Crops
Field Crops Foundation and Certified
Buffel grass, Dharaf grass, Guinea grass 80
Marvel grass, Stylo 90
Dinanath grass, Setaria grass,Tobacco 95
Groundnut 96
Sorghum, Sesame, Rapeseed, Mustard, Minor
millet, Taramitra, Jute, Forage Sorghum
97
Rice, Wheat, Maize, Pearl millet, Oat, Barley, Pea,
Triticale, Moong, Urd, Chickpea, Lentil, Pigeon pea,
Rice bean, Cow pea, Horse gram, Indian bean,
Niger, Lathyrus, Kidney bean, Rajmash,
Clusterbean, Soybean, Linseed, Safflower,
Sunflower, Castor, Cotton, Berseem, Indian clover,
Lucern, Teosinte
98
Napier grass (root cutting by number) 99.5

Minimum Seed Certification Standard for Pure Seed
Percentage Recommended in Vegetable Crops
Field Crops Foundation and Certified
Amaranth, Carrot 95
Asparagus, Spinach, Sugarbeet 96
Celery, Parsely 97
All Cucurbits (Pointed and Little Gourd), Cabbage,
Cauliflower, Chinease Cabbage, Turnip, Brinjal,
Capsicum, Chilli, Rat Tail Radish, Tomato, Lettuce,
Raddish, Fenugreek, Onion
98
Okra 99

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
Objectionable Weed Seeds

Maximum Seed Certification Standard for Total no.
of Objectional Weed Seed in Field Crops
Crops ObjectionableWeed Foundation Certified
Paddy Wild rice (O. sativa var. fatua) 2 5
Wheat,
Triticale
Wild morning glory (Hiran khuri;
Convolvulus arvensis) and Gulli danda
(Phalaris minor)
2 5
Rapeseed,
Mustard,
Taramira
Mexican prickly poppy (Satyanashi ;
Argimone mexicana)
5 10
Safflower Wild safflower (Carthamus oxyacantha) Nil Nil
Sunflower Wild safflower (Carthamus oxyacantha) Nil Nil
Lucerne Dodder Cuscuta spp.) 5 10
Berseem Chicory (Kasni; Cichorium intybus) 5 10
Oat Wild oat (Avena fatua) 2 5

Maximum Seed Certification Standard for Total no.
of Objectional Weed Seed in Vegetable Crops
Crops ObjectionableWeed Foundation Certified
Bittergourd Jangli karela (M. diocia), Nil Nil
Cucumber Cucumis hardwickii Nil Nil
Watermelon
Wild okra (Abelmoschus fioulneus, A.
manihot and A. moschatus)
Nil Nil
Okra
Wild okra (Abelmoschus fioulneus, A.
manihot and A. moschatus)
Nil Nil
Amaranthus
Wild amaranthus (Kantewali chaulai;
Amaranthus spinosus)
10 20
Fenugreek Senji (Melilotus spp.) 2 5
Lettuce Wild lettuce (Lactuca scariola) 2 2

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
Cause physical admixture with the crop seed only when
these crop mature approximately at the same time when
seed crop matures
Other crop seeds (Expressed in number/kg)

Maximum Seed Certification Standard for no. of
Other Crop Seed per kg in Field and Fodder Crops
Crop Foundation Certified
Castor, Groundnut, Safflower, Sunflower,
Rajmash
Nil Nil
Chickpea, Field pea, Rice bean Nil 5
Soybean, Horsegram Nil 10
Maize (Composite, Synthetic, OPV), Sorghum,
Lentil, Pigeon pea, Urd, Moong, Lathyrus, Bean,
Kidney, Cotton, Forage Sorghum
5 10
Rice,Wheat, Pearl millet, Minor millets, Barley,
Triticale, Oat, Rapeseed, Mustard, Taramira,
Jute, Linseed, Niger, Teosinte, Berseem, Stylo,
Lucerne, Cluster Bean, Indian clover, Marvel
grass
10 20
Buffel, Dharaf, Guinea and Setaria grass 20 40

Maximum Seed Certification Standard for no. of
Other Crop Seed per kg in Vegetable Crops
Crop Foundation Certified
Indian Bean, Brinjal, Lettuce, Bitter Gourd,
Bottle Gourd, Indian Summer and Winter
Squash, Pumpkin, Ridge Gourd, Snake Gourd,
Water Melon
Nil Nil
Okra Nil 5
Cucumber, Little Gourd, Musk Melon, Long
Melon, Capsicum, Tomato, Cabbage, Cauliflower,
Onion, Carrot, Radish, Turnip, Chilli, Sugarbeet,
Amaranth,Asparagus, Celery, Parsley, Spinach
5 10
Fenugreek 10 20

It refers to the diseases specified for the certification of
seeds and for which certification standards are to be met
with. These diseases would cause contamination, when
they are present in the seed field or within the specified
isolation distance (eg. loose smut of wheat). For this the
certification distance has been prescribed as 180 meters.
Designated diseases

Designated Disease of Field and Vegetable Crops
Crop Designated Disease Causal Organism
Barley Loose smut Ustilag nuda
Paddy Paddy bunt Neovossia horrida
Wheat
Loose smut
Karnal bunt
Ustilago tritici
Neovossia indica
Sorghum Grain smut, Kernel smut Sphacelotheca sorghii
Pearl millet Grain smut, Green ear, Ergot
Tolyposporium penicillariae, Sclerospora
graminicola, Claviceps microcephala
Mustard Alternaria blight Alternaria sp
Sesame Leaf spot Alternaria sp
Brinjal Little leaf DaturaVirus 2
Chillies Anthracnose leaf blight, Leaf blight Gloesporium piperatum,Alternaria solani
Cucurbits Mosaic Cucumis virus
Cowpea Anthracnose Colletotricum sp
Okra Yellow vein mosaic HibiscusVirus 1
Potato Brown rot, Root knot
Pseudomonas solanacearum, Meloidogyne
incognita
Tomato Early blight Leaf spot
Alternaria solani, Xanthomonas
vesicatoria

Designated Disease of Field and Vegetable Crops
Crop Designated Disease Causal Organism
Wheat Loose smut Ustilago tritici
Sorghum Grain smut, Kernel smut Sphacelotheca sorghii
Pearl millet Grain smut, Green ear, Ergot
Tolyposporium penicillariae, Sclerospora
graminicola, Claviceps microcephala
Mustard Alternaria blight Alternaria sp
Sesame Leaf spot Alternaria sp
Brinjal Little leaf DaturaVirus 2
Chillies Anthracnose leaf blight, Leaf blight
Gloesporium piperatum, Alternaria
solani
Cucurbits Mosaic Cucumis virus
Cowpea Anthracnose Colletotricum sp
Okra Yellow vein mosaic HibiscusVirus 1
Potato Brown rot, Root knot
Pseudomonas solanacearum,
Meloidogyne incognita
Tomato Early blight Leaf spot
Alternaria solani, Xanthomonas
vesicatoria

Determination of Other Distinguishable Varieties
“ODV testing is to estimate the number of seeds of other
distinguishable varieties present in a seed lot of designated variety”.
The determination is valid only if the cluster is stated by
the sender of the sample and if the authentic standard
sample of the cultivar is available for comparison in the
laboratory.
The determination shall be made only on the basis of readily
apparent differences in the stable and well-known
morphological characters of the seed.
Whenever difference is not clearly distinguishable or it has
occurred due to other physiological factors, such as frost, drought,
immaturity, storage or due to any other reasons which have
affected size, shape and luster of the seed the Seed Analyst should
not classify these seeds as ‘ODV’.

I. Work Board, Magnifier, Stereoscopic Microscope, Spatula and
Forceps.
II.Authentic samples of the notified cultivars of different crops
and vegetable seeds.
This determination must be made before
conducting the physical purity analysis
Materials Required

Procedure
Working Sample: The whole
submitted sample must be used for
marketing the determination. The
Analyst should, therefore, weigh the
submitted sample and record the
weight on the analysis card.
The sample should be examined
under magnification to determine the
number of seeds of the other cultivar
present in the sample.

The results of the investigation are expressed as the number
of seeds belonging to the other cultivar found in the actual
quantity examined.
In addition, the number per unit weight (e.g. per kg) may be
calculated.
Reporting the results
The actual weight of the seed examined and the number of
the seeds of the other cultivar present in the sample shall be
reported on the Analysis Certificate.
Calculation and expression of the results

The object of the test is to determine the
weight of 1000 pure seeds from the
submitted sample
Determination of TSW
"The thousand-seed weight (TSW) is the weight of 1000
pure seeds from the submitted sample"
Pure seeds are counted and weighed by one of two methods:
i) Counting the whole pure seed fraction
ii) Counting replicates of 100 seeds

Seeds can be counted:
• using a counting machine
• manually
• using a counting tool, e.g. counting boards or a vacuum
planting head
Apparatus Required
Vacuum Counting Head
Seed Counter

 The working sample consists of the whole pure seed
fractions for a purity analysis
 The whole pure seed fraction or replicates can be counted
either using counting machines or manual counting
(a) Weigh the whole pure seed fraction in grams to the
minimum no. of decimal places
(b) Count 100 seeds each in 8 replicates and weigh each
replicate in gram to the minimum no. of decimal places
Procedures

Weight of 1000 seeds = Weight of sample x 1000
No. of seeds counted
 Calculate the weight of 1000 seeds from the weight of the
whole pure seed fraction
Weight of 1000 seeds = Ʃ Weight of 100 seed replicates x 10
No. of 100 seed replicates
 Calculate the average weight of 1000 seeds from the
weight of 8 or more 100 seed replicates.
The result of TSW test must be reported under
“Other Determinations” with the minimum no. of
decimal places