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

Results:
Examine plates for charac-
teristic pathogen colonies,
beginning on the third day
and continuing through the
eighth day of incubation.
Also examine seeds under
a stereobinocular microscope.
View spores and
other fungal structures
under a compound microscope
to distinguish the
fungal forms. Express results
as a percentage of
seeds infected.
Washing test
General: Detects identifiable spores
on seed surfaces.
Procedure: 1. In a convenient vessel
(beaker or flask), place the
working sample and add
water, with or without a wet
ting agent, or alcohol.
Shake vigorously to remove
organisms adhering to the
seed surface.
2. Transfer washings into centrifuge
tubes and centrifuge
for about 5 min at low
speed (3000-5000 rpm).
3. Decant excess liquid from
each centrifuge tube and
examine extracted material
under a compound microscope
for fungal spores,
hyphae, and nematodes.
4. Stain with lactophenol blue
to color spores and hyphae
and thus detect fungi more
easily.
Results: Use a haemocytometer to
count the number of
spores.
6.3 Agar plate
showing ten evenly
spaced rice seeds.
Growing-on test
General: Detects seedborne fungal,
viral, and bacterial pathogens
which are readily
transmittable.
Procedure: Sow seeds on a suitable
medium (sterilized soil,
sand, or water agar) under
optimal conditions for germination
in order to detect
symptoms of infection that
are not normally detected
by other methods.
Isolation
Seedborne fungi can be conveniently isolated
using standard
mycological techniques.
Procedure: 1.Pick up actively growing
mycelia or spores with a
sterile needle under aseptic
conditions.
2. Inoculate mycelia or spores
on petri plates or slants
containing the appropriate
agar medium.
3. Incubate at 28 °C.
Identification
Identify fungi after viewing them under a
stereobinocular microscope
at different magnifications.
Procedure: 1. Prepare slide mounts of
spores or other bodies
in a drop of water or
lactophenol blue and examine
under a compound microscope
for shape, size,
and color.
2. Compare findings with
those on pp. 75-89 and
with literature available on
fungal taxonomy (Booth
1977; Ellis 1971, 1976;
Ou 1985; Raper and
Fennell 1977; Raper and
Thom 1984; Sutton 1980).
28 Rice seed health testing manual