Mechanism Of Herbicidal Action Of The Component From Pythium Aphanidermatum

Pythium aphanidermatum PA1 was isolated from Lolium perenne L., Pythium spp was a destructive pathogen,and the toxin of Pythium spp had good herbicidal activtity.In this study,the macrorption was used to separate the herbicidal component from the fermentation broth of Pythium aphanidermatum,then the optomum adsorption condition was researched.At the same time,the herbicidal mechanism of the component from Pythium aphanidermatum was tested.1.The adsorption of the herbicidal component from the fermentation broth of Pythium aphanidermatum on a series of macroporous adsorption resins HPD400, HPD500, HPD600, HPD700, HPD850, ADS-17, D101 and DM130 was studied. The herbicidal component was confirmed by HPLC analysing the residue and the effluent.The component with retention time of 4.550min was determined with herbicidal activity preliminary,the semiproeparative chromatography Nove-pak-C18 column was used in purification at 254 nm ,then the component confirmed had herbicidal activity.2.Among the 8 resins used,HPD500 was the best resin for the adsorption of the herbicidal component. The optimum adsorption conditions for HPD500 were: adsorption temperature, 20℃; feed volume, 33.75 mL/g; feed rate, 2 BV/h. The adsorbed herbicidal component was eluted with 2.5 BV of 10% ethanol with an elution rate of 1 BV/h.3.The herbicidal mechanism of the component from Pythium aphanidermatum was tested in this research. The effect on inhibition of seed germination and growth was determined and the MDA content, superoxid anion radical content, hill activity, root activity were examined. The length of root was inhibited under illumination, while the inhibition on the stem length under darkness was higher, the relative electric conductivity under illumination were 94.55μS/cm, 58.75μS/cm, whereas the relative electric conductivity under darkness were 85.25μS/cm, 36.25μS/cm, respectively, the MDA content of Digitaria sanguinalis L.and Chlorella pyrenoidosa under illumination were 0.08385, 0.1742, 0.0129, 0.01935 under darkness, superoxid anion radical content and hill activity under illumination were higher under illumination, simultaneously, These results showed the photosynthesis was affected by herbicidal component from Pythium aphanidermatum.4. In order to know the pathogenesis of Pythium aphanidermatum to Lolium perenne L.The chlorophyll content,β-carotene content, PSâ…¡, the MDA content, superoxid anion radical content, hill activity, root activity and relative water content were examined.The results showed that chlorophyll,β-carotene were destroyed, Fv/Fm, Fm became lower ,the F₀ of Nuspeedâ…¡was not changed,but the F₀ of Inspire became higher,the MDA content and superoxid anion radical content became higher and the hill activity with the concentration of toxin increasing,and root activity and relative water content were also affected.