Pathogen Identification And Biological Characteristics Of Cynanchum Chinense R.Br. Leaf Spot Disease

Cynanchum chinense R.Br. belongs to Cynanchum, Asclepiadacea. It is a kind ofperennial herb mostly growing on non-agricultural lands like coastal and wilderness places.Most plants of this gennus can be medicine directly. The extracts of its juice also can resisttumor which has great development potential on the research of wild drugs. After a seriesresearches about the Cynanchum chinense R. Br. grow on the seasides and beaches of Dalian.The author found the Cynanchum chinense R. Br. which grow on wild places mostly hasfungus diseases. But the species and identification of these fungus diseases is rarely reported.This paper shows the investigation and identification of fungus diseases on the Cynanchumchinense R. Br. in Dalian. In order to providing the basis for the planted Cynanchum chinenseR. Br., the author also conduct a series of studies on the pathogen indentification andbiological characteristics of its leaf spots.(1)Most Cynanchum chinense R. Br. have leaf spot disease in wild conditions whichprimordially appears on June and becoming serious from August to September.Accroding to the survey in2011, its disease index and incidence are63.3and96.7%.While on2012, the data shows69.1and100%. The white rot diease also appears. We alsofound two insects, Aphis nerii and Tropidothorax elegans Distant. The density of Aphis neriiis higer which can be more harmful.(2)Four fungi are separate from the leaves infected leaf spot. The single spot separationrate of UN-P1and UN-P2are68.18%and6.82%. The infection experiments proved thatUN-P1and UN-P2can both lead to the pathogenesis of inoculated leaves no matter infectionalone or mixed. This suggested the pathogens of Cynanchum chinense R. Br. are UN-P1andUN-P2. Fungal common substrates ITS1and ITS4are used to sequences the rDNA-ITS ofUN-P1and UN-P2. After constructing the phylogenetic trees and the comparision ofhomology, the UN-P1is proved to be Rhizoctonia solani and the UN-P2is Nigrosporasphaerica which matches the results of morphological indentification.(3) UN-P1: Mycelia can grow from15℃to30℃; the optimum growth temperature was24℃; lethal temperature is63℃; the optimum pH is7; the optimum humidity50%. Myceliarapid growth period is about48-108hours. Dark environment can make mycelial grow well; the optimum carbon source was sucrose; nitrogen source is urea, the most suitable inorganicsalt was NaH2PO4, and the optimum growth factor is vitamin B1.UN-P2: Mycelia can grow from5℃to30℃; the optimum growth temperature was24℃; lethal temperature is68℃; the optimum pH is8; the optimum humidity90%. Myceliarapid growth period is about48-108hours. Dark environment can make mycelial grow well;the optimum carbon source was D-fructose; nitrogen source is yeast, the most suitableinorganic salt was K2HPO4, and the optimum growth factor is naphthyl acetic acid. UN-P2can sporulate in15℃-35℃, optimal sporulation temperature is24℃; light environment isbetter for sporulatio. Mycelial growth rate slowed down after four days, and the sporulationcontinued to increase. Spore germination optimum temperature is25℃; the optimum pH is8,the optimum humidity is90%. Dark environment is suitable for spore germination.