The Physiological Race Specialization Of Cucumber Downy Mildew In Heilongjiang

Cucumber downy mildew,caused by Pseudoperonospora cubensis(Berk.& M.A.Curtis) Rostovzev,is the most common and destructive disease of cucumber.In the warm and humidity condition,the reproduction and spread of the pathogen are rapidly,and the disease may destroy entire plants of susceptible varieties,cause heavy losses in short periods of time.The study consisted of these parts:(1)study on the morphological observation and measurement of sporangia of P.cubensis.(2)study on the virulence identification of P.cubensis.(3)RAPD analysis of P.cubensis from different areas.(4)ITS analysis of P.cubensis from different areas.The 20 isolates could be devided into 5 pathotypes based on virulence on the 9 identified host, they areâ… :Pc-hb2,Pc-hb3,Pc-qq1,Pc-qq3,Pc-md1,Pc-dq2,Pc-da3,Pc-hh2,Pc-hh3,Pc-hh4,Pc-hh5;â…¡: Pc-jm1,Pc-dq1,Pc-hh1;â…¢:Pc-hb1,Pc-qq2;â…£:Pc-hb6;â…¤:Pc-hb4,Pc-hb5,Pc-hb7.DNA of P.cubensis from 7 cities of Heilongjiang province were successfully extracted by CTAB method,RAPD analysis showed that the relationship of 25 isolates were not close,and genetically complex.There was relationship between RAPD analysis and their origin.Most of the isolates from the same city were close and genetic similarity.Using the established system,all the 31 genomic DNA samples could obtain an approximate 900bp,which collected from different regions of Heilongjiang Province.According the sequence measurement and the analysis:The germ stub ITS area many Tais and of geography source relativity with certain existence,the relative relation of the most germ from same city source is nearer;Come from black river of of the germ stub Pc-hh 1 with Pc-hh 3 with all germ stub heredity distance farther,this with its geography position also have a certain relation;But different city germ's relation between many Tais and geography source of the germ stub ITS area of the source have no regulation,namely and not city geography position is apart from more near,it is relative to relate to more near;The germ from Mo river stub Pc-mh1 have no obvious difference with other germ stubs.