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

Detection
Blotter and agar plate methods are
standard tests. The washing test reveals
identifiable spores or mycelia
adhering to or growing on the seed
surface. Thc growing-on test is a
supplementary test to detect readily
transmittable seedborne pathogens.
Blotter method
General: This standard test is a simple
and inexpensive way to
detect seedborne fungi that
respond to sporulation. During
routine seed health
testing at IRRI, this procedure
satisfactorily detects
important seedborne fungal
pathogens. Data in Tables
6.1-6.3, indicate the varying
frequencies of detection
among some common rice
pathogens from 1987
to 1990 at the Seed Health
Unit.
Procedure: 1.Use 9.5-cm petri plates
made of Pyrex glass or
clear plastic to allow NUV
light to penetrate. The
plates should contain
2-3 layers of good-quality
white or colored blotter papers
moistened with distilled
water (Fig. 6.2a).
2.Place seeds rom the working
sample, (with or without
pretreatment) equidistant
on the petri plates at
25 seeds/plate (Fig. 6.2b).
3. Incubate seeds at 22 °C
under a 12-h light and 12-h
dark cycle with NUV light for
6-8 d (Fig. 6.2c). (See
Chapter 3 for light source
specification and other
details.)
Results: Express results as a percentage
of the number of
total seeds.
Table 6.1 Percent incidence of seedborne pathogens on untreated outgoing seed lots received
for certification by the IRRl Seed Health Unit, 1987-90. a
Pathogen
1987 1988
Affected Detection Mean
seed lots levels value
91.4 1-92
Alternaria padwickii
Aphelenchoides besseyi b 3.3 1-134
Curvularia spp.
88.1 1-69
Sarocladium oryzae
71.8 1-70
Microdochium oryzae 31.8 1-17
Fusarium moniliforme 11.3 1-5
Drechslera oryzae
19.3 1-16
Pyricularia oryzae
0.2 1
Tilletia barclayana
3.2 1-60
Pathogen
Alternaria padwickii
Curvularia spp.
Sarocladium oryzae
Microdochium oryzae
Fusarium moniliforme
Drechslera oryzae
Pyricularia oryzae
Tilletia barclayana
Aphelenchoides besseyi b
17.8
6.8
6.0
3.0
1.1
1.4
1.0
6.3
15.3
Affected Detection Mean
seed lots levels value
97.9
93.1
78.1
36.9
12.0
23.1
0.4
9.3
6.8
1989 1990
Affected Detection Mean
seed lots levels value
99.2 1-81
92.2 1-71
71.8 1-70
41.3 1-18
14.4 1-19
25.1 1-25
0.1 1
11.9 1-84
7.6 1-712
23.5
8.1
4.3
2.2
1.5
1.4
1.0
12.1
13.9
1-92 22.2
1-79 12.6
1-63 6.5
1-49 2.6
1-13 1.3
1-28 1.9
1 1.0
1-98 12.0
1-107 9.8
Affected Detection Mean
seed lots levels value
95.4
88.5
68.5
61.2
32.5
18.5
0.5
4.8
6.4
1-98
1-79
1-66
1-24
1-17
1-14
1
1-57
1-73
40.6
7.9
4.5
3.3
1.6
1.7
1.0
4.4
6.5
a Based on 200 seeds per seed lot. No. of seed lots examined: 1325 (1987), 1600 (1988), 1703 (1989), 2373
(1990). b Actual nematode count.
Table 6.2 Percent incidence of seedborne pathogens on untreated incoming seed lots received
for postentry clearance by the IRRl Seed Health Unit, 1987-90. a
Pathogen
54.0
Alternaria padwickii
Aphelenchoides besseyi b 19.9
Curvularia spp.
78.7
Sarocladium oryzae
26.1
Microdochiurn oryzae 22.1
Fusarium moniliforme 10.7
Drechslera oryzae
Pyricularia oryzae
46.3
7.0
Tilletia barclayana
15.8
Pathogen
1987 1988
Affected Detection Mean
seed lots levels value
1-69
1-783
1-40
1-29
1-4
1-41
1-39
1-93
1-544
1989
9.8
12.5
4.2
6.2
1.3
7.9
8.4
14.3
69.0
Affected Detection Mean
seed lots levels value
Alternaria padwickii
91.2 1-93 21.5
Curvularia spp.
83.2 1-59 12.3
Sarocladium
Microdochium
oryzae
oryzae
54.3
29.5
1-81
1-28
6.2
3.2
Aphelenchoides besseyi b 15.8 1-204 11.3
Fusarium moniliforme 25.2 1-25 2.2
Drechslera oryzae
Pyricularia oryzae
81.0
2.2
1-72
1-17
9.8
2.7
Tilletia barclayana
17.1 1-99 12.2
Affected Detection Mean
seed lots levels value
92.7
91.0
31.8
13.0
12.3
73.7
0.9
19.2
7.3
1-95
1-75
1-40
1-9
1-13
1-88
1-2
1-84
1-9
1990
27.8
11.3
4.2
1.4
1.5
6.9
1.3
14.9
2.1
Affected Detection Mean
seed lots levels value
78.9
88.9
39.5
45.2
28.0
64.0
0.8
14.9
23.4
1-88
1-80
1-24
1-68
1-10
1-52
1-2
1-88
1-58
28.1
7.2
3.3
4.4
1.7
6.7
1.5
20.3
7.6
a Based on 200 seeds per seed lot. No. of seed lots examined: 272 (1987), 422 (1988), 457 (1989), 261 (1990).
b Actual nematode count.
26 Rice seed health testing manual