Untitled - International Rice Research Institute

Detection frequency (%)
90
80
East Asia
Europe
Latin America
South Asia
Southeast Asia
Sub-Saharan Africa
70
60
50
40
30
20
10
0
Detection level (%)
35
30
25
20
15
10
5
0
1990 1991 1992 1993 1994 1995 1996 1997
Year
Fig. 24. Detection frequency (a) and level (b) of Pyricularia oryzae from imported untreated seeds, 1990-97.
Colony characters on culture media (Fig. 27)
Colonies on PDA at ART (28–30 °C) grow very
slowly and attain a 3.04-cm diam in 5 d. They are
azonated, slightly felted, with aerial mycelia that are
white with brownish gray portions, even margins, and
with about 1-mm advancing mycelia submerged.
Saltation of colonies is observed in some plates. The
colony on the reverse side of the agar plate is zonated
and black, turning light outward. At 21 °C under
alternating 12-h NUV light and 12-h darkness, colonies
grow very slowly and attain a 2.17-cm diam in 5
d. They are zonated, slightly felted with even margins,
and brownish gray. The colony on the reverse
side of the agar plate appears zonated and black with
a lighter color outward. At 28 °C under alternating
12-h fluorescent light and 12-h darkness, colonies
grow very slowly and attain a 2.78-cm diam in 5 d.
They are azonated and become zonated toward the
margin, floccose to slightly felted. Aerial mycelia are
white with brownish gray portions. The colony on the
reverse side of the agar plate is azonated and becomes
zonated near the margins, and appears white
with greenish gray centers.
Colonies on PJA at ART (28–30 °C) grow very
slowly and attain a 2.87-cm diam in 5 d. They are
azonated, becoming zonated toward the margins,
velvety, becoming granular with age, with 0.8-cm
submerged advancing mycelia, gray to light gray
29