Studies On Bio-Activitie Of Compounds From Plant Extract Against Magnaporthe Grisea

Rice blast is one of the most serious diseases in rice production area in the world. Long-term use of chemical pesticides has threatened safety of environment,food security and drug-resistant pathogens,and these problems have aroused wide concern.Therefore, it is particularly important for developing botanical pesticides against Rice blast.This study was find a active compound from plant extracts which has better control effect against Rice blast,and meanwhile inhibition mechanism of the active compound was investigated at a fundamental level.16 plant extracts were extracted from 16 plant species of herbal medicine through different solvents.All plant extracts were tested on leaf segments.The results showed when plant extracts were tested with concentration of 10g/L,the effect against Rice blast was more than 50%,in which Wyz,Sj,Cp and Bx effect was observed as high as more than 90%;and effect was followed by Mx,Cyc,Th1,Dc,Hq and Hj,which were more than 80%;At the concentration of 5g/L,Mx,Cp,Wzy,such as 12 kinds of plant extracts effect were more than 50%.266 separate flows were obtained from 16 kinds of plant extracts.All separate flows were tested on leaf segments.The results indicated as followed:at the concentration of 0.33g/L,Zzj-1,Sj-2,Cyc-2,such as 34 eparate flows effect were hyper 60%.Whilst at concentration of 0.165g/L,control effect shows that the Hq-5 has the highest effect, which amounted to 75.6%;Zzj-3,Cyc-2,Dc-5,such as 7 separate flows effect was more than 40%.Though TLC,HPLC,LC-MS analysis,Hq-5 was combined with 3 compounds, Hq-5A,Hq-5B and Hq-5C.Chrysin and Wogonin had been identified while structure of Hq-5C needed further identification.Biological activity of 3 compounds showed that:at concentration of 0.165g/L,Hq-5C has the highest effect,which was more than 70%, Hq-5A and Hq-5B have lower effect.So,we are determined Hq - 5C as the main active compound.Through toxicity determination for Hq-5C,the value of EC₅₀ is 150.85mg/L.Growth rate method was used to determine control inhibiting of mycelium growth about Fusarium graminearum,Sclerotinia sclerotiorum,Botrvtis cinerea,Rhizoctonia solani,Bioplaris oryzae,Colletotrichum cocodes.The results indicated that at the concentration of 200mg/L,there were only 34%～42%inhibiting effect on Botrvtis cinerea,Sclerotinia sclerotioru-m,Fusarium graminearum,Bioplaris oryzae.Cotyledon method was measured by Hq-5C.At the concertration of 165mg/L,the control effect on cucumber cotyledon was 88.73%.Whether there are effects to other 5 diseases of Hq-5C has to be studied further.When using histological dyeing method to test inhibition mechanism of compound Hq-5C,the results showed that:8h after inoculation,there were no significant inhibition against conida germination and appressorium formination.But Hq-5B and Hq-5C produced dilutus appressorium compared with CK.36h after inoculation,the infection hypha formation rate of Hq-5C and CK were 2.72%,99.33%,respectively.The conclusion was that,the control effect of compound Hq-5C against Rice blast was inhibited infection hypha formation by reducing the formation of melanoma.