Study On Sclerotina Stem Rot Of Ligusticum Chuanxiong

Ligusticum chuanxiong belongs to Umbelliferae of Ligusticum.It is famous mainland medicinal materials in Sichuan province,it is grown in Sichuan province,Southwest,East, North China and so on.The Ligusticum chuanxiong sclerotinia stem rot was severity disease in Du-jiangyan basement of Sichuan province.In 2007,the percentage of the disease reached 10%～30%,the serious was 50%,which caused the decline and death of the Ligusticum chuanxiong.The dissertation included the symptom characteristics,the identification of pathogen,the biological characteristics,the fungicides screening in Laboratory for Ligusticum chuanxiong sclerotinia stem rot and the main control methods.1 The sympyom characteristics and scathe of Ligusticum chuanxiong sclerotinia stem rotThe original symptoms indicated dark brown hygrophanous splotch appeared on the basal leaves and indicated dark brown circular spot appeared on the base stems.Finally,the whole plant stopped growing and died.White mycelium or sclerotia was formed when the conditions was too wet.In 2007,the percentage of the disease reached 5.14%～41.67%,the average was 20.67%and the serious reached 54.21%in Du-jiangyan Ligusticum chuanxiong basement of Sichuan province.2 Cultural characteristics of Ligusticum chuanxiong sclerotinia stem rotThe pathogen was cultured on PDA medium,the colony was white,gossypine,and some dark brown globular shapes appear circled the colony later.The dark brown globular shapes began to form into sclerotias after 8 days.The sclerotias were black,circular or irregular-shaped,with diameter of 2～5mm.3 Inoculation and identificationThe diseased symptom and the pathogen characteristics of inoculated plant,were similarly to the diseased plant in field.It was improved that the isolate was the pathogen of Ligusticum chuanxiong sclerotinia stem rot.After the morphological characteristics and the sequence of ribosomal DNA-ITS,the pathogen was identified as Sclerotinia sclerotiorum(Lib.)de Bary.4 Biological characteristicsThe mycelia[Sclerotinia sclerotiorum(Lib.)de Bary]of Ligusticum chuanxiong sclerotinia stem rot could grow better on PSA and millfeed medium than others and product more sclerotias on millfeed medium than others.The optimum temperature and the pH value were separately at 25℃and 7～8.The optimum carbon source and nitrogen source were sucrose and sodium nitrate.The effect of light on mycelia and ascospore growth was not evident.The range of temperature for ascospore germination was 10～30℃.5 Disease cycleThe main way of pathogens spread was wind and rain.The results demonstrated that ascospore could infect independently leaves or stems of Ligusticum chuanxiong. Microscopic observation on the infection process of Ligusticum chuanxiong leaves by Sclerotinia sclerotiorum(Lib.)de Bary showed that the germinal tube of ascospore could invade into cell cavity,no penetration via stomata was observed so far in this study.6 Laboratory screeningThe results demonstrated that the best fungicides of inhibiting the mycelia growth were 70%thiophanate methyl and 40%Zhigao,the second were 50%carbendazim and 40%Junhejing.The results demonstrated that the best fungicides of inhibiting the sclerotia germination were 40%Junhejing,70%thiophanate methyl.The best fungicides of inhibiting ascospore germination were 40%Junhejing,the worst was 50%carbendazim.7 Study on biocontrol potential of the microparasite fungi in sclerotiaA strain was isolated from the interior of the surface-disinfested sclerotia,which was thought to have greater biocontrol potential against sclerotinia sclerotiorum.The strain was identified as Trichoderma aureoviride according to Rrfai's classification system of Trichoderma.The dual culture of strain T.aureoviride and S.sclerotiorum on a cellophane strip indicated that Trichoderma hyphal parallel and touch to those of S.sclerotiorum,which could overgrow the colony of the pathogen,infecting sclerotia and making them rot.The volatile metabolites had only an inhibition to the number and size of sclerotia,such as they could make sclerotia decrease.