The Effects Of Organic Amendments On Cotton Verticillium Wilt And Their Mechanism To Control Disease

The control effects of eight kinds of organic amendments on cotton Vert id Ilium wilt were investigated in squaring, boll and harvest stage respectively in pot and plots. Chitin (crab shell powder) was the best in three times of investigation and the effect in harvest stage was 72.21%, beanstalk powder was the second with the 60.02% effect, the effects of green manure (fresh oilseed leaves) and rice chaff were 54.38% and 49.02%, and the others weren't good to control cotton Verticil Hum wilt. The similar result in plot experiment was obtained, and the effects of chitin, beanstalk powder, green manure and rice chaff were 62.26%, 58.78%, 51.68% and 44.17%, and the others were not effective to control the disease.The mechanism of microecology, biochemistry and direct inhibition was studied in this experiment. 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 for each treatment were different. There were more fungi species in the66rhizosphere 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 etc. , but Mucor hi emails, Rhizopus nigricans, Stachybotrys chartarum and Penicillium viridicatum were dominates in the rhizosphere after applying peanut cake and poultry manure. Normally, the more the strain number of bacteria and actinomycetes in the rhizosphere were, 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 Vert idIlium dahliae in the rhizosphere for better-effect treatments was higher than that of worse-effect ones and CK.The contents of binary phenols and dissolvent sugars in cotton were changed in some degree after organic amendments were applied. The relationship between the control effects of organic amendments and the contents of binary phenols in cotton was positive , but the relationship between the control effects and dissolvent sugars in cotton was uncertain.The direct inhibition of lixivium of organic amendments to the growth of mycelium, germination of spore and microsclerotium of Verticil Hum dahliae was measured in vitro. The results indicated that the. lixivium of different organic amendments could inhibit67Verticillium dahliae in different degrees. This showed that there is unknown substance that can inhibit the pathogen in lixivium, the direct inhibition of organic amendments to cotton Verticillium dahliae is also one aspect of the mechanism to contol disease.