Untitled - International Rice Research Institute

Detection frequency (%)
120
100
East Asia
Europe
Latin America
South Asia
Southeast Asia
Sub-Saharan Africa
80
60
40
20
0
Detection level (%)
100
80
60
40
20
0
1990 1991 1992 1993 1994 1995 1996 1997
Year
Fig. 10. Detection frequency (a) and level (b) of Bipolaris oryzae from imported untreated seeds, 1990-97.
16.10 µ (PDA); 4–11 septate, 43.47–101.43 µ ×
12.19–16.10 µ (PSA); and 5–11 septate, 59.80–
106.03 µ × 10.12–16.33 µ (MEA).
Colony characters on culture media (Fig. 13)
Colonies on PDA at ART (28–30 °C) grow slowly
and attain a 3.38-cm diam in 5 d. They are azonated
with sinuate margins, hairy at the center, becoming
cottony toward the margin, yellowish gray at the center
and gray toward the margin, and becoming grayish
olive with age. The colony appears azonated and
black on the reverse side of the agar plate. At 21 °C
under alternating 12-h NUV light and 12-h darkness,
colonies grow very slowly and attain a 2.38-cm diam
in 5 d. They are fluffy, azonated with uneven margins,
with olive gray aerial mycelia, becoming dark
olive gray outward. The colony on the reverse side of
the agar plate appears azonated and black. At 28 °C
under alternating 12-h fluorescent light and 12-h
darkness, colonies grow very slowly and attain a
2.53-cm diam in 5 d. They are fluffy with nil to
scanty aerial mycelia, azonated with uneven margins,
and olive black with 3.0-mm light gray advancing
mycelia. The colony appears azonated and black
with light gray margins on the reverse side of the
agar plate.
Colonies on PSA incubated at ART (28–30 °C)
grow moderately fast and attain a 4.48-cm diam in 5
d. They are fluffy, azonated with sinuate margins,
and grayish yellow at the center, becoming dark olive
gray outward. The colony appears azonated and olive
black to black on the reverse side of the agar
19