The Pathogen Isolation,identification And Fungicides Screening Of Physalis Alkekengi L. Root Rot In Laboratory

In recent years,with the change of Physalis Alkekengi L. planting from the wild to cultivated, Physalis Alkekengi L. Root Rot become more and more serious. It has been one of limitations of Physalis Alkekengi L Production. In this paper,pathogen of Physalis Alkekengi L. Root Rot was identified and biological characteristics,chemical control were studied.First, the author collected 56 disease roots and isolated 110 fungals from the growing areas of Physalis Alkekengi L. in Yilan County of Heilongjiang Province.7 fungal species were identified from these isolates, Fusarium solani, Fusarium oxysporum ,Fusarium tricinctum, Fusarium acuminatum, Fusarium lateritium and two kinds of Penicillium. The separation frequency of five pathogens are 34.55%,26.36%,13.34%,7.27% and 16.18%.The results showed that Fusarium solani and Fusarium oxysporum are the main pathogen of Physalis Alkekengi L. Root Rot.To further identify the taxonomic status of pathogenic bacteria. The rRNA gene sequence of filamentous fungi was amplified by PCR using fungal universal primers Its1 and Its4.The PCR products were sequenced to identify the fungal species. The results showed that Fusarium solani and Fusarium oxysporum are the main pathogen of Physalis Alkekengi L. Root Rot.The results of the biological studies on Fusarium solani and Fusarium oxysporum showed that the favorable medium is PDA medium.But the light is less effect on them.25℃and pH 8 is the optimum condition for Fusarium solani ;and 30℃and pH 7 is the optimum condition for Fusarium oxysporum.Using the toxicity of seven fungicides and its concentrations were determined by testing the conidial germination rate and colony growth. The results indicated that conidial germination rate was effeetively inhibited by 75% Chlorothalonil, 60% Carbendazim,Root rot stop and 50% Different bacteria urea . The best effect reach 100% by 60% Carbendazim and Root rot stop.The EC₅₀ of two kinds of fungicides were 2.78 mg/L and 2.33 mg/L for Fusarium solani;and the EC₅₀ of two kinds of fungicides were 2.34mg/L and 13.96 mg/L for Fusarium oxysporum.For Fusarium solani,60% Carbendazim: Root rot stop (3:7) have synergy ;and for Fusarium oxysporum , 60% Carbendazim: Root rot stop(7:3) have synergy. These ratio have obvious synergy.