Maize seedlings (Liao No. 613) were cultivated under controllable
greenhouse conditions at a temperature of 20–25 C and
relative humidity of 80–90%. At the three leave stage, maize seedlings
were divided into three groups, each of which included thirty
seedlings. The conidiospores of Bipolaris maydis were collected and
diluted as 1 104 conidia ml1. A CHM1 culture solution
(1.6 107 cfu ml1) was obtained after incubation at 30 C,170 rpm
for 36 h, was diluted two fold (mixed with distilled water at 1:1 to
decrease the density to 8 106 cfu ml1) and then evenly sprayed
on the surface of maize leaves. After 6 h, the maize leaves were
inoculated by evenly spraying with the conidiospores of B. maydis.
The seedlings were first cultivated in the dark overnight at 24 C
and 98% relative humidity and then cultivated in a growth chamber
with 16-h-light and 8-h-darkness cycle at 24 C and 85% relative
humidity (Mu, 2000). Each treatment, in triplicate, was arranged in
a completely randomized block with 3 30 plants. Spraying with
diluted LB medium and conidiospores of B. maydis served as
a negative control, and spraying with distilled water served as
control. After pathogen challenge, the disease was observed every
2 days. Disease index and protection effect by CHM1 were visually
rated by assessing the percentage of leaf surface covered by disease
spots