| Daylily is a perennial perennial herb flower,which has strong tolerance to alkaline soil,drought,semi-shade,water humidity,noise and dust.After hundreds of years of development,it has cultivated many fine varieties with beautiful flowers and beautiful posture,and has become an important gardening plant and family gardening flower in many places.Like most garden plants,daylily is threatened by various diseases during cultivation,among which,leaf blight has been increasing in recent years,which is not conducive to the innovation of daylily germplasm resources and greening applications.In this study,a field investigation on leaf blight of daylily was conducted,and on this basis,the pathogenic bacteria were isolated and identified.At the same time,the biological characteristics of the pathogenic bacteria were investigated and the indoor fungicide screening study was conducted.The main results are as follows:1.Five spot sampling method was used to conduct field investigation in daylily germplasm resource nursery in Shanghai.The investigation showed that the incidence rate of daylily leaf blight was different in different plant row spacing conditions.The plant row spacing was 15cm×15cm,the incidence rate of daylily was 20.74%,and the disease index was 23.94.With the increase of plant row spacing,the incidence rate and disease index showed a downward trend,and the plant row spacing was 30cm×30cm.The incidence rate of daylily was only 8.16%,and the disease index was 12.15.The incidence rate of daylily under different cultivation conditions was investigated.The incidence rate of daylily under field cultivation conditions was 15.03%,and the disease index was 19.48;The incidence rate of daylily under shading net cultivation was 13.33%,and the disease index was 8.89;The incidence rate of daylily cultivated in greenhouse was 8.72%,and the disease index was 8.72.The investigation results of incidence rate in different growth cycles showed that the incidence rate and disease index were: Evergreen daylily>Semi evergreen daylily>Deciduous daylily.The investigation results of incidence rate of daylily leaf blight of different varieties show that the variety with the highest incidence rate is’ Longfields Think Pink ’,the incidence rate is 58.97%,and the disease index is 39.74.Secondly,the incidence rate of ’On Patrol’,’Decoy’,’Paprika’,’Broaddway Jazz’,’Chinese Mountain’ and’Ephemera’ are all above 50%,and the disease index is 23.89,55.45,25.90,53.33,21.18 and 50.00 respectively.The varieties with the lowest incidence rate are ’Mary’,’Rajah’,’SIT Pink Power’,’SIT Pink Sweetheart’,’Longfields Twins’,’ Lemon Electra ’,’All American FHief ’,’ Den of Iniquidity ’,’ Silicon Double Classic ’,’ Water Water Everywhere ’,’ Navel Assaullt ’,’ Nowhere to Hide ’,H.fulva(introduced in Jiuhe Township,Lijiang),’ Stellar Double Rose ’,’ Cyberha wk ’,’ Darla Anita ’ Incidence rate of ’Multiverse’,’Kiss of Paradise’ and ’String Bikini’ have basically no symptoms.2.Pathogens were isolated from the leaves of susceptible plants,and the isolated and purified pathogens were named D-1 and D-3.Observation shows that on the culture medium,the D-1 colony is in the form of white cotton wool,with fluffy edges,plump and dense hyphae,and the spores are in spindle shape,with sizes ranging from7.08～12.58μm×2.24～3.23μm.D-3 colony is white and purple cotton-like,the edge is fluffy,the hypha is full and dense,the spore shape is spindle,the size is7.36～9.05μm×2.58～4.25μm.The genomic DNA of the two strains D-1 and D-3 were amplified by ITS1/ITS4 primers,and the r DNA-ITS sequences of D-1 and D-3 were obtained respectively.The phylogenetic analysis results showed that D-1 and Fusarium avenae were clustered into one branch,and D-3 and Fusarium tricinctum were clustered into one branch,which were far from other strains.Through morphological observation and ITS sequence analysis of the strains,it was preliminarily determined that the two isolates D-1 and D-3 were Fusarium avenae and Fusarium tricinctum.3.The pathogenicity of the two isolates D-1 and D-3 was verified by leaf grafting.After 7 days of inoculation,the two groups of leaves were all diseased,and the morphology of the disease spot was similar to that of the natural disease in the field.The diseased leaves were re-separated and cultured,and the morphological characteristics of the isolated strains were also consistent with the original inoculated strains,completing the validation of Koch’s rule.4.The effects of culture medium,pH value,light intensity,and lethal temperature on the mycelial growth of two pathogenic bacteria D-1 and D-3 were studied.The results showed that D-1 could grow in PDA,PSA,BEP,SDA,and WA,and grew best on PDA medium,with a colony diameter of 69±0.15mm;It can grow between pH4～10,and the optimal growth environment is pH6～7.The bacterial colony diameter is 68.8±1.53 mm and 57.5±0.93mm;The growth of the colony was the best under 24 hours full darkness illumination,with a diameter of 86.5±1.00mm;The lethal temperature of the mycelium is 80 ℃(10min).D-3 can grow in PDA,PSA,BEP,SDA,and WA,and grows best on BEP medium,with a colony diameter of40.25±0.95mm;D-3 can grow between pH4～10,and the optimal growth environment is pH7～8,with colony diameters of 42±2.52 mm and 39±1.61mm;The growth of the colonies was the best under 24 hours full darkness illumination,with a diameter of67.3±0.21mm;The lethal temperature of the mycelium is 60 ℃(10min).5.The screening results of indoor control agents showed that D-3 and D-1 had different sensitivity to 15 different fungicides,and D-3 was the most sensitive to 40%flusilazole,30% pentazo carbendazim and 45% prochloraz;The sensitivity to 50%Pythicarb,75% Chlorothalonil and 70% Thiobacillus methyl is the weakest.D-1 was the most sensitive to 45% prochloraz,30% pentazo carbendazim and 12% mesobiotin;The sensitivity to 70% thiophanate-methyl,75% chlorothalonil,77% cupric calcium sulfate,80% mancozeb,and 50% humicin was the weakest. |
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