| Pepper blight is a devastating fungal soil-borne disease caused by Phytophthora capsici,has seriously affected the yield and quality of pepper and become a major problem in the production of pepper.Because of environmental pollution and pesticide residues,chemical control of pepper phytophthora blight is restricted.Biological control has received attention because of its human,environmental,ecological health and safety,and has become an important means of prevention and control of soil borne diseases.Bacillus BS211 strain preserved in our laboratory was used in this study.Effect of BS211 incubation condition on production of antimicrobial substances,label of rifampicin-resistance for BS211 and its colonization in the pepper rhizosphere,effect of BS211 suppressing Phytophthora capsici in potcapsici andtheefficiency of BS211 controlling Pepper Phytophthora Blighthave been studied in greenhouse..Firstly,the effect of liquid culture conditions on the antagonistic substance produced from BS211 was studied in indoor conditions.The results showed that the sterile filtrate from BS211 can inhibit the growth of Phytophthora capsici.The sterile filtrate at different time from different liquid culture medium showed different antibacterial activity,the antibacterial substance content produced from PN culture medium was highest and the antibacterial substance content produced from LB liquild culture medium was lowest.The antibacterial activity decreased firstly and then increased and decreased further,and the content of antibacterial substance was highest at 4h after culturing.Secondly,the study of screening of rifampicin-resistance for BS211 and its colonization activity in the pepper rhizosphere were conducted.And five mutant strains of BS211 that showed stable resistant against rifampicin were obtained,wherein the mutant strain BS211-B4rif-r has no significant difference with the wild strain BS211 in colony morphology and antibacterial activity against Phytophthora capsici.Although the growth rate and the capacity of spore producing of mutant strain was lower than that of wild strain,but the difference was not significant.The mutant strain BS-11-B4rif-r showed better capacity of colonization in pepper rhizosphere.The population of mutant strain BS211-B4rif-r in substrate and soil was decreased from 2×107 cfu/g and 8×107 cfu/g to 7.83×106 cfu/g and 4.27×106 cfu/g respectively after 50 days,and it showed better colonization ability as compared with other bacteria strains as reporetd.In order to exploring the effect of BS211 on controlling pepper phytophthora blight furtherly,the effect of BS211 on controlling pepper phytophthora blight under different cultivation media in pot and the effect of bioorganic fertilizer,that containing BS211 as the core strain,on controlling pepper phytophthora blight in field were studied.The results showed that the control effects were 30%in sterilized substrate and 24%in sterilized soil.The results from detecting microbial population showed that the amount Bacillus of the treatment BS211 has 2.7×106 cfu/g matrix and 6.35×106 cfu/g soil in pepper rhizosphere,the control treatment has 0.16×106 cfu/g matrix and 0.16×106 cfu/g soil.In addition,the number of Phytophthora capsici in BS211 treatment decreased 36%in substrate and 22%in soil.When the concentration of Phytophthora capsici was low(200 spores/g soil),bioorganic fertilizer has 95 to 100%effect on controlling Pepper Phytophthora Blight;and after the second inoculation of Phytophthora capsici(600 spores/g soil),bioorganic fertilizer has a bad effect on controlling Pepper Phytophthora Blight,but there was still 2.41～83.33%.The pepper phytophthora blight showed sooner and higher incidence along with the increasing population of Phytophthora capsici.The combining treatment of ammonium hydrogen carbonate-nitrification inhibitors can increase the content of ammonium nitrogen and decrease the nitrate content,which reducing Phytophthora capsici popultaion,and the treatment of ammonium hydrogen carbonate decrease the content of ammonium nitrogen and have higher Phytophthora capsici population.The pH of combined treatment was significantly higher than other treatments,and the electrical conductivity was significantly lower than other treatments.Pot experiment showed that the disease index rise slowly at 7～19d after transplanting and rise fasterly at 19～30d after transplanting.The control effect of NH4HCO3-DMPP treatment was 53.33～58.89%,and that of NH4HCO3 treatment was 15.56～32.22%. |
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