The Effects Of Organic Absjects On Cucumber Downy Mildew

The cucumber downy mildew is a common disease of cucumber and cause serious loss.In order to guarantee the unharmful control of cucumber downy mildew In this study,we investigated the control effects of seven kinds of organic amendments on cucumber downy mildew,futher explored the mechanism of control disease.The control effects of seven kinds of organic amendments on cucumber downy mildew were investigated in the harvest stage in plots.Chitin(crab shell powder)was the best and the effect in harvest stage was 62.23%,beanstalk powder was the second with the 58.76%%effect,the effects of green manure(fresh oilseed leaves)was 51.60% %,others were not effective to control the disease.The mechanism of microecology was studied after treatment with organic amendments.Experimental results showed that the population of fungi,bacteria and actinomycetes in soil and rhizosphere was increased remarkably after applying organic amendments.The rhizosphere fungi species,species number and dominates with diferent treatments were different.There were more fungi species in the rhizosphere after applying organic amendments that had better control effects.The fungi dominates in the rhizosphere after applying chitin and beanstalk powder were Stachybotrys Chartarum,Penicillium viridicatum,Paecilomyces lilacinus,Myrothecium roridum and Acremonium kiliense.But Mucor hiemalis,Rhizopus nigricans,Stachybofrys chartarum,Penixillium vridicatum were dominates in the rhizosphere after applying peanut cake,poultry manure and control treatment.Normally,the more the strain number of bacteria and actinomycetes in the rhizosphere,the better the control effects of organic amendments were.The inhibition of rhizosphere fungi and actinomycetes for different treatments was measured in vitro.The results indicated that the rate of inhibiting microbes to downy mildew in the rhizosphere for better-effect treatments was higher than that of worse-effect ones and CK.The direct inhibition of lixivium of organic amendments to the growth of mycelium,germination of zoospores of Pseudoperonospora was measured in vitro.The results indicated that the lixivium of different organic amendments could inhibit Pseudoperonospora in different degrees.This showed that there is unknown substance that can inhibit the pathogen in lixivium,the direct inhibition of organic amendments to cucumber Downy mildew is also one aspect of the mechanism to contol disease.These results indicated that the organic amendments reduced the amount of the primary innoculoum in soil through improving the rates and the amounts of fungi and actinomycetes with inhibition effects in soil and rhizosphere,or by drect inhibition to Pseudoperonospora.The contents of binary phenols and dissolvent sugars in cucumber were investigated after treatment with organic amendments The relationship between the control effects of organic amendments and the contents of binary phenols in cucumber was positive,but the relatonship between the control effects and dissolvent sugars in cucumber was uncertain.