Untitled - International Rice Research Institute

orange. On the reverse side of the agar plate, the
colony looks azonated and yellowish brown. At 21 °C
under alternating 12-h NUV light and 12-h darkness,
colonies are restricted in growth and attain a 3.96-cm
diam in 15 d. They are azonated, plane, velvety with
even to slight sinuate margins, pale orange, and
moisture is produced with age. The colony on the
reverse side of the agar plate appears azonated and
yellowish brown. At 28 °C under alternating 12-h
fluorescent light and 12-h darkness, colonies are restricted
in growth and attain a 4.23-cm diam in 15 d.
They are zonated, plane, velvety with sinuate margins,
and pale orange. On the reverse side of the agar
plate, the colony appears slightly zonated and yellowish
brown.
Colonies on PSA at ART (28–30 °C) are restricted
in growth and attain a 4.80-cm diam in 15 d.
They are slightly zonated, slightly felted with sinuate
margins, and pale orange. The colony on the reverse
side of the agar plate appears slightly zonated and
pale yellow-orange. At 21 °C under alternating 12-h
NUV light and 12-h darkness, colonies are restricted
in growth and attain a 4.21-cm diam in 15 d. They
are azonated, plane, slightly velvety, with a few
slight radial furrows, sinuate margins, and pale orange.
The colony appears azonated, with a few radial
wrinkles and pale yellow-orange on the reverse
side of the agar plate. At 28 °C under alternating 12-h
fluorescent light and 12-h darkness, colonies are restricted
in growth and attain a 4.05-cm diam in 15 d.
They are slightly zonated, slightly felted with a few
slight radial furrows in some plates, with slightly sinuate
to even margins, and pale orange; moisture is
produced with age. The colony appears slightly zonated
with a few slight radial wrinkles and pale yellow-orange
on the reverse side of the agar plate.
Colonies on MEA at ART (28–30 °C) are restricted
in growth and attain a 4.84-cm diam in 15 d.
They are slightly zonated, plane, velvety, and pale
orange. The colony appears slightly zonated and dull
orange with pale yellow-orange margins on the reverse
side of the agar plate. At 21 °C under alternating
12-h NUV light and 12-h darkness, colonies are
restricted in growth and attain a 4.37-cm diam in 15
d. They are zonated, felted with slight sinuate margins,
and pale orange. On the reverse side of the agar
plate, the colony appears azonated and dull orange
with pale yellow-orange margins. At 28 °C under
alternating 12-h fluorescent light and 12-h darkness,
colonies are restricted in growth and attain a 4.47-cm
diam in 15 d. They are plain to felted, zonated at the
center, and become azonated toward the margins,
with slight radial furrows and slight sinuate margins.
Colonies are pale orange and whitish toward the margins.
On the reverse side of the agar plate, the colony
appears zonated with a few radial wrinkles and dull
orange with pale yellow-orange margins.
Seedborne fungi causing grain and inflorescence diseases in rice
Curvularia sp.
Disease caused: black kernel
a. Symptoms
Black discoloration on grains.
b. Occurrence/distribution
Curvularia sp. is frequently isolated from discolored
rice grains. Several species have been reported
on rice from different countries (Fig. 38),
but C. lunata and C. geniculata are the most common
ones.
c. Importance in crop production
Curvularia sp. causes little or no yield loss under
normal rice production situations. Infected grains,
after being polished, may produce black kernels,
thus reducing their market value.
Detection on seed
a. Incubation period on blotter
On blotters incubated under NUV light at 21 °C,
the fungus can be observed growing on rice seed
7 d after seeding. The detection frequency is
about 70.6% on seeds coming from different regions
(Fig. 39a,b).
b. Habit character
Aerial mycelia are scanty or absent; if present,
they are light brown to brown with abundant
branching. Conidiophores are solitary or in groups;
dark brown; straight, sometimes bent; simple;
arising directly from the seed surface. Conidia are
borne more or less at the tip in a whorl or in thick
panicles (Fig. 40a-c).
38