Plants were inoculated with B. oryzae after 35 days
(emergence of the eighth leaf from the main tiller)
(Matsuo and Hoshikama 1993) in hydroponic culture.
Plants were inoculated with the isolate CNPAF-HO 82 of
B. oryzae. This isolate was preserved on pieces of filter
paper in glass vials with silica gel at 4°C. Pieces of filter
paper containing the fungus were transferred to Petri
dishes with potato-dextrose-agar (PDA). After 3 days,
PDA plugs containing fungal mycelia were transferred to
new Petri dishes containing PDA. These Petri dishes were
kept in a growth chamber at 25°C with a 12-h photoperiod
for 10 days. A conidial suspension of B. oryzae (5×10 3
conidia ml -1 ) was applied as a fine mist to the leaves of
each plant until runoff using a VL Airbrush atomizer
(Paasche Airbrush Co., Chicago, USA). Gelatin (1%, w/v)
was added to the sterile water to aid conidial adhesion to
the leaves.
Plants were grown under greenhouse conditions with
temperature of 30±5°C during the day and 18±2°C during
the night; the maximum photon irradiance on the plant
canopies was about 900 μmol m -2 s -1 until the day of
inoculation. Immediately after inoculation, plants were
transferred to a mist chamber at 25±2°C with an initial
24 h dark period. After this 24 h period, plants were
incubated using a 12 h photoperiod of photon irradiance
≈ 225 μmol m -2 s -1 provided by cool-white fluorescent
lamps. The relative humidity inside the mist chamber was
approximately 95±2% throughout the experiment. Plants
were kept inside the mist chamber for the duration of the
experiment.