A manual of rice seed health testing - IRRI books - International Rice ...

elevant tests for determining the
incidence of weed seed contamination
are purity analysis and determination
of other species by number.
To obtain a composite sample, see
Chapter 4.
Purity analysis
One of the objectives of this test is to
determine the identity of the various
species of seeds and inert particles in
thc sample.
The working sample is separated
into three component parts: pure
seeds, other seeds (identified by
their Latin names), and inert matter.
The percentage of each part is determined
by weight, calculated to one
decimal place. Components of less
than 0.05% are reported as trace.
Determination of other
species by number
The objective of this test is to determine
the number of seeds of other
species. This test is used mainly to
determine the presence of noxious or
undesirable seeds (e.g., weed seeds).
The working sample (minimum
500 g for rice) is examined either for
seeds of all other species (complete
test) or of certain designated species
(limited test). The number of seeds
found of each species sought is
counted.
The result is expressed as the
number of seeds belonging to each
designated species or category found
in the actual quantity examined. In
addition, the number per unit
weight (e.g., per kg) may be calculated.
The actual weight of seed examined,
its Latin name, and the number
of seeds of each species sought and
found shall be reported on the
Analysis Certificate. The certificate
should be endorsed as a complete test,
or a limited test, or a reduced test (if
the whole working sample was not
examined).
Weed seeds encountered during
dry seed inspection are listed and
briefly described in Table 12.1 and
are shown in Figures 12.1-12.12.
12.7 Seeds of
Echinochloa colona
(courtesy of
K. Moody and
R. Lubigan).
12.8 Seeds of
Echinochloa crusgalli
ssp. hispidula
(courtesy of
K. Moody and
R. Lubigan).
12.9 Seeds of
lschaemum rugosum
(courtesy of
K. Moody and
R. Lubigan).
12.10 Seeds of
Panicum repens
(courtesy of
K. Moody and
R. Lubigan).
12.11 Seeds of
Paspalum distichum
(courtesy of
K. Moody and
R. Lubigan).
12.12 Seeds of
Rottboellia
cochinchinensis
(courtesy of
K. Moody and
R. Lubigan).
66 Rice seed health testing manual