Study On The Chemical Fungicides And Pantoea For The Control Of Summer Patch On Kentucky Bluegrass

Summer patch is a stubborn soil-borne disease on Kentucky bluegrass,and its scientific and practical control has always been a concern for turfgrass disease researchers.In this thesis,Magnaporthiopsis poae,the primary pathogen causing summer patch,was selected as the study target.Fungicide azoxystrobin and propiconazole,and seven strains of endophytic bacteria（which have been proved to be able to control rice blast on rice）were used to analyze their control efficiency in vitro and in vivo,to provide reference and theoretical basis for the scientific control of summer patch on Kentucky bluegrass.The specific results of this study are as follows:1.The results of M.poae sensitivity to azoxystrobin and propiconazole showed that 14strains of Magnaporthiopsis poae were sensitive to azoxystrobin EC₅₀ values ranged from0.09μg/m L to 0.22μg/m L.Three strains（LT103,MP120 and MP102）showed decreased sensitivity to propiconazole,ranging from 0.95μg/m L to 1.30μg/m L,eight strains（MP56,MP4,MP177,MP102,MP2,MP126,MP28 and LT98）were sensitive to propiconazole,and their EC₅₀ values ranged from 0.14μg/m L to 0.34μg/m L.Pot experiments were conducted to investigate the control efficiency of azoxystrobin application methods for summer patch.The results showed that the best application method was the first spraying 1 day before paroxysm.The second spraying 15 days after the first spraying,and the control efficiency by this method was as high as 95.95%.Four propiconazole sensitive strains（MP56,MP4,MP177 and MP102）and two strains（MP103 and MP120）with reduced sensitivity to propiconazole were selected for the pot experiment.The results showed that propiconazole had excellent control efficiency on the four sensitive strains,ranging from 61.11%to 100%.The control efficiency on the two strains with reduced sensitivity were 5.56%（MP120）and15.00%（MP103）,respectively.The results of propiconazole against M.poae in vitro and in vivo were consistent.2.7 bacteria were screened for growth promotion and control effect in Kentucky bluegrass.The growth promotion of screened bacteria would be verified in soil.Seven strains of bacteria（LTE3,LYY2b,LLE3a,LLE11,LMT2b,LYE4a and LTE5a）could significantly improve the germination rate and gravitropism of Kentucky bluegrass,and increase root hair length,root hair number,leaf length,surface area,average diameter and volume,root length,surface area,average diameter and volume.The plate confrontation test showed that all strains except LTE5a had a excellent inhibitory effect on M.poae mycelial growth.The inhibition rates ranged from 49.07%to 94.96%,and the inhibition rates of LTE5a to different M.poae strains were low,ranging from 2.52%to 41.96%.The control efficiency of the six bacteria on different M.poae strains were determined in vivo.The results showed that LTE3and LYY2b were superior to other bacteria to control M.poaes.The relative control efficiencies of LTE3 ranged from 90.96%to 100%,and those of LYY2b ranged from 91.55%to 99.55%.LTE3 and LYY2b were also superior to other bacteria in promoting the growth of Kentucky bluegrass both above-ground and under-ground.Furthermore,the effects of LTE3and LYY2b on the development of Kentucky bluegrass were investigated in soil experiment.The results showed that LTE3 and LYY2b significantly increased the fresh weight,rhizosphere soil,leaf number,leaf length,leaf surface area,leaf average diameter,leaf volume,root length,root surface area,root average diameter and root volume of Kentucky bluegrass.3.The control efficiency of LTE3 and LYY2b and propiconazole at different concentrations（1μg/m L,5μg/m L and 10μg/m L）on summer patch of Kentucky bluegrass were compared in vivo on plates.The results showed that the control efficiency of LTE3 and LYY2b on summer patch and growth promotion of Kentucky bluegrass were better than those of propiconazole applications.The relative control efficiency range of LTE3 was 93.88-100%,and the relative control effect range of LYY2b was 94.47-100%.5μg/m L and 10μg/m L propiconazole treatments showed excellent control efficiency on the sensitive M.poae strains,with a range of 73.23%to 100%.However,the control efficiencies of the M.poae strains with reduced sensitivity to propiconazole was poor.Their relative control efficiency range is0%to 21.26%on the last day.The percentage of leaf yellowing of Kentucky bluegrass reached 100%when treated with 10μg/m L propiconazole,while no leaf yellowing occurred in the treatments only inoculated with LTE3 or LYY2b.The under-ground and above-ground growth of Kentucky bluegrass treated with LTE3 and LYY2b were better than those of propiconazole treatments.Among the three application concentrations,5μg/m L of propiconazole treatment showed the best comprehensive effects on the control of propiconazole-sensitive strains,promoting the growth of Kentucky bluegrass and avoiding drug damages when compared with 1μg/m L and 10μg/m L of propiconazole treatment.Furthermore,the control efficiency of LTE3,LYY2b and propiconazole at 5μg/m L on summer patch of Kentucky bluegrass were compared in soil experiment.The results showed that bacteria LTE3 had the best control efficiency on all M.poae strains with different sensitivities to propiconazole,and on promoting the growth of Kentucky bluegrass,followed by the bacteria LYY2b.The propiconazole treatment only had better control efficiency on the four propiconazole sensitive strains of M.poae,the control efficiency on the two M.poae strains with reduced sensitivity to propiconazole was poor,and the growth-promoting effect on Kentucky bluegrass was not significant.