Bioactivity Screening Of Plant Extracts On Magnaporthe Grisea

Rice blast, caused by the heterothallic ascomycete Magnaporthe grisea, is one of the most severe diseases of rice worldwide. Much money is paid to contral it. M.grisea acquire new variation and get resistance to chemical fungicide very easily. To overcome the disadvantage of pedticide resistance and environment pollution by having been sprayed chemical fungicide, developing and utilizing the metabolite of plant to control it is a hot point in fungicide research.117 plant extracts were extracted from 101 plant species in 50 families through ethanol,aether,petroleum,chloroform and so on. Then they were tested against M.grisea by the method of spore germination and of leaf segment.Result showed that 92 plant extracts could inhibit germination of conidium and 7(S1-Gp1,Jq-Z1,Xg-Zst et al) plant extracts could inhibit appressorium formation of M.grisea entirely though they couldn't inhibit germination of condium by 100% at 100-times dilution. 26 (Mh-C1,Wzy-Gs1,Sz-Gs7 et al) plant extracts could inhibit germination of conidium and 30 (Hj-Z1,Bh-Lj1,Tmd-Kj1 et al) plant extracts could inhibit appressorium formation at 500-times dilution. 16 (Xfy-G3,Sj-Gj2,Bl-Gs1 et al) plant extracts could inhibit germination of conidium and 8 (Jx-G7,Sz-Gs6,Jz-Z21 et al) plant extracts could inhibit appressorium formation at 1000-times dilution.When plant extracts were tested on barley leaf segments, inhibition efficiency of 19(Bz-G6,Jx-G7,Thl-G1 et al) plant extracts were higher than 80% at 50-times dilution. The inhibition of Sjc-C2,Mx-G3,Sj-Gj2 and Thl-G3 were higher than 80% at 200-times dilution, 94.44%,81.31%,80.23% and 77.40% respectively at 500-times dilution, and 84.85%,77.41%,52.53% and 70.7% at 1000-times dilution.When plant extracts were tested on rice leaf segments. The inhibition of Sjc-C2 and Mx-G3 were 89.87% and 79.74% respectively.Barley leaf was used to replace rice leaf when plant extracts were screened by method of leaf segments. To proved it is feasible, five chemical fungicides (Tricyclazole,Kasugamycin,Iprobenfos,Thiophanate-methyl and Salicylic acid) were selected treating barley and rice before inoculate M.grisea by method of leaf segments and pot seedling respectively. Disease severity was measured seven days after inoculation. Result showed that there exist a positve relativity between rice leaves and barley leaves, though the five compounds possess different mode of action on M. grisea. It is supposed a novel bioassay method by using barley leaf instead of rice leaf for screening plant extract against M. grisea...