A manual of rice seed health testing - IRRI books - International Rice ...
A manual of rice seed health testing - IRRI books - International Rice ...
A manual of rice seed health testing - IRRI books - International Rice ...
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Table 10.2. continued<br />
Disease<br />
Growth stage at which<br />
inspection is made a<br />
Scale (degree <strong>of</strong> severity)<br />
<strong>Rice</strong> tungro (RTV)<br />
<strong>Rice</strong> ragged stunt (RSV)<br />
See note in RTV.<br />
Grassy stunt (GSV)<br />
Note: Scale being developed.<br />
2<br />
(greenhouse)<br />
3-5<br />
(field)<br />
2-3<br />
(greenhouse)<br />
4-6 (field)<br />
2-3<br />
(greenhouse)<br />
3-6<br />
(field)<br />
Scale (based on symptom severity<br />
3 wk after inoculation)<br />
1 No symptoms<br />
3 1-10% plant height reduction,<br />
no distinct leaf discoloration<br />
5 11-30% height reduction; no<br />
distinct leaf discoloration<br />
7 31-50% height reduction and/or<br />
yellow to orange leaf discoloration<br />
9 More than 50% height reduction;<br />
and yellow to orange leaf<br />
discoloration<br />
Scale (based on symptom severity<br />
5 wk after inoculation)<br />
1 No symptoms<br />
3 0-10% plant height reduction; no<br />
short, ragged, or curled leaves<br />
5 0-10% height reduction; youngest<br />
normal leaves, 1-2 older leaves<br />
abnormal<br />
7 10-30% height reduction; with<br />
youngest normal leaves; may<br />
have 3-4 abnormal older leaves<br />
9 More than 30% height reduction;<br />
or with abnormal leaves including<br />
the youngest<br />
General scale can be used in the<br />
meantime<br />
0 No infection<br />
1 1-10%<br />
3 11-30%<br />
5 31-70%<br />
7 51-70%<br />
9 71-100%<br />
Sheath blight (ShB)<br />
Pathogen: Thanatephorus cucumeris<br />
( Rhizocotonia solani )<br />
Sheath rot (ShR)<br />
Pathogen: Sarocladium oryzae<br />
7-8<br />
7-9<br />
Scale (based on relative lesion<br />
height)<br />
0 No infection observed<br />
1 Lesions limited to lower 20% <strong>of</strong><br />
the plant height<br />
3 20-30%<br />
5 31-45%<br />
7 46-65%<br />
9 More than 65%<br />
Scale (incidence <strong>of</strong> severely affected<br />
tillers)<br />
0 No incidence<br />
1 Less than 1%<br />
3 1-5%<br />
5 6-25%<br />
7 26-50%<br />
9 51-100%<br />
Field inspection 55