| Oilseed rape is a common oil crop broadly planted in China.Sclerotinia rot of colza induced by Sclerotinia sclerotiorum is the main disease which can decrease the oilseed rape yield..As the sclerotinia rot of colza has a wide range ofhost species as well as tenacious vitality,and also can spreadeasily,there is no effective control method except for using chemical pesticides.However,the use of chemical pesticides over the years has caused great damage to both human beings and the natural environment,which further makes it more difficult to prevent and cure the disease.Therefore,an effective and environment-friendly method for treat sclerotinia rot of colza is urgently required to be explored.Recently,biological control protocol has drawn much attention by developing bioantibacterial agents aiming at effectively disinfecting sclerotinia rot of colza.This thesisfocuses on the separation and screening of biocontrol actinomycetes antagonisticaly against Sclerotinia sclerotiorum from soils.And the control efficacy,growth promoting effect and separation of active substances were studied.The main findings are:Seventeen strains systemically screened from 150 actinomycete strains had an antagonistic effect on Sclerotinia sclerotiorum.Particularly,5 strains demonstrated strong antagonistic activity,identified as Actinomycete DXM-7074,GB-026,SWX-027,GB-024 and GB-001,respectively.The diameters of the inhibition zone of these strains were more than 20 mm.The inhibitory rates of mycelial growth rate of sterile fermentation broth SWX-027,GB-001,GB-026 and DXM-7074 were 69.17%,65.85%,67.07% and 73.17%,respectively.DXM-7074 and GB-026 were selected as the antagonistic bacteria.Based on the culturing morphologies,physiological and biochemical experiments of GB-026 strain coupling with 16 S rDNA sequencing,Strain GB-026 was similar to Streptomyces sampsonii strain ATCC 25495 with the similarity of 99%.The phylogenetic tree indicated that it was in the same branch with Streptomyces sampsonii and Strain GB-026 was determined to be a member of Streptomyces sampsonii.The anti-disease effect of these actinomycetes was conducted indoor.Both the actinomycete DXM-7074 and GB-026 can significantly control the spread of the disease plaque by filling the root with the bacterial fluid or spraying seedling leaves and detached blades with bacterial fluid.Actinomycetes DXM-7074 showed the better disease prevention effect.In vitro leaf experiment demonstrated that the pathogens were inoculated at different times on the leaves,and showed a similar diameter of the lesion indicating that there wasno obvious difference.These results showed that the control effect of actinomycete DXM-7074 and actinomycete GB-026 on leaves was stable.The control efficiency of the sprayed actinomycete DXM-7074 and actinomycete GB-026 was 43.71% and 31.13%,respectively.The control efficiency in the case of filling roots by using the actinomycete DXM-7074 and GB-026 was 29.82% and 10.53%,repectively.In the field experiment,the control efficacy of actinomycete DXM-7074 was above 30% for both 7 and 15 days.In general,actinomycete DXM-7074 showed better efficacy than actinomycete GB-026.After filling root with the bacterial fluid or spraying leaves with fermented fluid,fermented liquid filling root treatment with actinomycete DXM-7074 could obviously promote the dry weight of stem and leaf,with the 42.37% growth rate of dry weight compared to the control group.Filling root treatment on root with actinomycete GB-026 had the promoting effect on its fresh weight with the growth rate of 27.59%.The effect of the two strains on the growth of oilseed rapes rape was not significant without any obvious difference.The filling root treatment with actinomycete DXM-7074 on oilseed rapes could significantly increase the enmyzitic activity of PPO by 29.3%.By exploring the fementation procedure,it is desirable to optimize the fermention condition of actinomycete GB-026 for carrying out plenty of fermentation amount.And it is also benifited to extract and separate more active species from the bulk fermentation system. |
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