Studies On Pathogen Identification And Disease Control Of Major Fungal Diseases On Bletilla Striata

Bletilla striata is a kind of orchid with high medicinal and ornamental value.In recent years,its demand has risen year by year in the market,many places began to develop artificial planting vigorously.But with the continuous expansion of planting area,various diseases occurred frequently,and led to the decline of yield and quality,which seriously affected the sustainable development of the industry.There are few systematic studies on fungal diseases on B.striata so far.In order to provide a certain theoretical basis for the control of fungal diseases on B.striata,pathogeny etiology,screening and application of biocontrolstrain and fungicides were carried out in this study.The main results are as follows:1.Disease investigation and pathogen identification.Five kinds of fungal diseases were found,of which rust disease and leaf brown spot disease were the most important fungal diseases,their range was wide and the damage was serious;Secondly,leaf spot disease of seedlings and tuber rot disease occurred locally,but the disease would lead to the whole plant death directly.The grey mould disease occurred in the field sporadically,which was less harmful.Through the isolation and purification,pathogenicity determination,morphological and molecular biological identification of culturable pathogen,the pathogen of leaf brown spot disease was identified as Fusarium avenaceum,the pathogen of leaf spot disease of seedlings was identified as F.equiseti,the pathogen of tuber rot disease was identified as F.solani,the pathogen of grey mould was identified as B.cinerea,the unculturable pathogen of rust disease was identified as C.bletilla.2.Biological characteristics of pathogens causing major fungal diseases.The optimum growth temperature of F.avenaceum?HGUP17355 strain?was 20?and the optimum pH was 6.It grows the fastest on OMA.When maltose was used as carbon source and L-phenylalanine was used as nitrogen source,the utilization ratio was the highest,and the lethal temperature was 45?for 10 min;The optimum growth temperature and pH of F.equiseti?HGUP17361 strain?were28?and pH7,respectively.It grows the fastest on PSA.The growth rate of strain was the highest when sucrose was used as carbon source and beef extract as nitrogen source,and the lethal temperature was 50?for 10 min.The optimum growth temperature and pH of F.solani?HGUP1833 strain?were 28?and pH 7,respectively.The growth rate of strain was the fastest on PSA.The utilization rate was the highest when sucrose was used as carbon source and monarkite as nitrogen source,and the lethal temperature was 50?for 10 min.The effects of different light treatments on the mycelium growth of the three pathogens were not significant.3.Screening and control of biocontrol strain.The four strains were labeled as MD1,MS5,X7and F4,respectively,which had strong inhibitory effect on the pathogens causing leaf brown spot disease,leaf spot disease of seedling and tuber rot disease.The order of inhibitory effect of each strain was MD1>MS5>X7>F4.Combined with morphological characteristics and molecular phylogeny of the strains,MD1 strain was identified as T.hamatum,MS5 strain as T.rossicum,X7and F4 strains as B.subtilis.Preparation of fermentation broth of four biocontrol strains for control of leaf brown spot disease in field,four strains had a certain field control effect on leaf brown spot disease.The relative control effect of Bacillus X7 was the best,and the control effect was 43.45%.4.Screening and control effect in field of fungicides.The results of indoor virulence test showed that the five kinds of fungicides?1%Genazinomycin SC,45%Prochloraz EC,37%Difenoconazole EC,30%Pyridamole EC,20%Pyrazole ether+10%Tebuconazole SC?were effective in inhibiting the pathogen causing leaf brown spot in laboratory,the EC₅₀0 were 3.068 3?6.235 6,13.526 3,36.431 6,45.682 9 mg/L;The four kinds of fungicides?45%Prochloraz EC,15%Difenoconazole+15%Propiconazole SC,Genazinomycin SC,30%Allicin EC?were effective in inhibiting the pathogen causing leaf spot disease of seedling in laboratory,the EC₅₀were 4.660 9,9.068 8,9.699 7,22.150 6 mg/L;The three kinds of fungicides?25%Oxime ester+50%Tebuconazole,1%Genazinomycin SC,30%Allicin EC?were effective in inhibiting the pathogen of tuber rot disease in laboratory,the EC₅₀0 were 1.141 5,3.394 0,18.065 8 mg/L.The results of control to leaf brown spot and rust disease in the field showed that the field control effects of 1%Genazinomycin SC and 45%Prochloraz EC to leaf brown spot disease were 71.15%and 67.61%,respectively.The field control effects of 25%Ketotriazole WP and 12.5%Ether ester+12.5%Fluoxazole SC to rust disease were 86.70%and 70.34%,respectively.5.The effects of different fertilizers on the occurrence of leaf brown spot and rust disease.Among the three kinds of biofertilizer,"GengTian biofertilizer"?treatment C?had certain effect on reducing the occurrence of brown spot and rust disease on B.striata,the disease index less37.23%and 22.3%than CK.The effect of five kinds of foliar fertilizer on reducing occurrence of the two diseases was not significantly different,and the control effect was lower,the effect of“CuiKang JingJia foliar fertilizer”?treatment D?was the best,the disease index was less 14.34%and 8.05%than CK.