Untitled - International Rice Research Institute
Untitled - International Rice Research Institute
Untitled - International Rice Research Institute
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Detection frequency (%)<br />
120<br />
100<br />
East Asia<br />
Europe<br />
Latin America<br />
South Asia<br />
Southeast Asia<br />
Sub-Saharan Africa<br />
80<br />
60<br />
40<br />
20<br />
0<br />
Detection level (%)<br />
35<br />
30<br />
25<br />
20<br />
15<br />
10<br />
5<br />
0<br />
1990 1991 1992 1993 1994 1995 1996 1997<br />
Year<br />
Fig. 34. Detection frequency (a) and level (b) of Sarocladium oryzae from imported untreated seeds, 1990-97.<br />
seed surface, rarely becoming aerial. Conidiophores<br />
are very short with conidia collected in a<br />
slime drop that are globose and shiny (Fig. 35a-c).<br />
c. Location on seed<br />
S. oryzae is mostly observed on the entire seed<br />
(about 46%) and on the lemma and/or palea<br />
(about 31%) (Fig. 36).<br />
Microscopic character<br />
a. Mycelia—white, sparsely branched, septate (Fig.<br />
35d).<br />
b. Conidiophores—slightly thicker than the vegetative<br />
hyphae, simple, or branched either once or<br />
twice; terminal branches tapering at the tip (Fig.<br />
35e).<br />
c. Conidia—hyaline, smooth, single-celled, cylindrical<br />
with rounded ends; straight, sometimes slightly<br />
curved, formed singly (Fig. 35f). Measurements:<br />
2.07–8.74 µ × 1.15–3.68 µ (PDA); 4.14–8.28 µ ×<br />
1.38–3.68 µ (PSA); and 4.14–7.13 µ ×1.38–3.91 µ<br />
(MEA).<br />
Colony characters on culture media (Fig. 37)<br />
Colonies on PDA at ART (28–30 °C) are restricted in<br />
growth and attain a 4.33-cm diam in 15 d. They are<br />
azonated, plane, velvety with even margins, and pale<br />
36