|
By the flagellated bacteria subphyla, Oomycetes, downy mildew Division, Cuba fake downy mildew [of Pseudoperonospora cubensisi (Berk.EtCurt) Rost] infection caused by cucumber downy mildew, cucumber production the most extensive, the most serious losses diseases. Cucumber downy mildew is a living body nutrition specifically obligate parasites, not artificial culture, thus limiting the in-depth study of cucumber downy mildew physiological differentiation, population genetic aspects. Try to ITS sequence analysis of the test method, with the RAPD analysis method and the traditional morphology (sporangia) variance analysis and pathogenic differences in analysis methods, and to explore the the Heilongjiang Province cubensis physiological species differentiation problem, the anti for cucumber disease breeding basis. The results are as follows: 20 strains of pathogenic measured, the results show that different strains of pathogenic different on the same host, there are obvious differences prove its toxicity. 20 strains of nine differential host reaction can be divided into five pathogenic type. Were group Ⅰ: Pc-hb2 the Pc-hb3, the Pc-qq1, the Pc-qq3, Pc-md1 the Pc-dq2, Pc-da3 the Pc-hh2, the Pc-hh3, the Pc-hh4, the Pc-hh5 II The group: the Pc-im1 of Pc-dq1, Pc-hh1; Ⅲ group: the Pc-hb1, the Pc-qq2; Ⅳ group: the Pc-hb6; Ⅴ group: the Pc-hb4, Pc-bbe the Pc-hb7. Collected from the bacteria source of toxicity in the same city, there is a greater difference. No correlation between bacteria toxicity and sporangium size and geographical origin. Using a modified CTAB method successfully extracted genomic DNA from seven cities in the province cucumber downy mildew. Cubensis and RAPD molecular markers, the results indicate low similarity among strains around due to the strong mutual choice between different cultivars, host and pathogen cubensis obligate parasitic bacteria produce abundant genetic diversity, there is a large variation. Correlation between certain strains RAPD polymorphism and geographical origin, a closer relationship between the majority source of the bacteria from the same city. The source of the bacteria taken from the same city on the shape, size and kinship are closer. Determined by screening cubensis ITS region amplification system optimization, and the amplification system of 31 strains of cucumber downy mildew, can be approximately 900bp fragment. Sequencing and analysis that: the existence of a certain correlation between the strain ITS region polymorphism and geographical origin, a closer relationship between the majority source of the bacteria from the same city: from Heihe strains Pc-hh1 and Pc- hh3 far all strains genetic distance and location also have a certain relationship: but no regularity strains ITS region polymorphism with the geographical origin of the relationship between different cities bacteria source, ie not city location nearer apart, the more kinship nearly; no significant differences from the strains of Mohe Pc-mh1 with other strains.
|