Study Of Genetic Diversity Of Valsa Mali In China Using SRAP And ISJ Markers

Valsa canker of apple, one of the most destructive stem diseases on apple tree in China, is caused by fungal pathogen of Valsa species. It is called"cancer of apple tree"by famers because of its vast distribution, destructive damage and difficulties of control. It was reported that there was differentiation among strains of Valsa mali on biological characteristics and pathogenicity. But no systematic study on genetic diversity of Valsa mali is reported till now, knowledge of Occurrence Regularity of the disease and Resistance Breeding is consequently limited. In the dissertation polymorphism of Valsa mali was analyzed using SRAP (Sequence-Related Amplified Polymorphism) and ISJ (Intron-Exon Splice Junction) markers. The results were obtained and described as below:1. 21 pairs of SRAP primers with high polymorphism and stability were sceened from 150 pairs.2. Amplified system of Valsa mali based on SRAP was established for the first time: 10×Reaction Buffer,2.5μL; MgCl2 (25 mM), 2.0μL; dNTPs (10 mM), 0.5μL; Forward primer (10μM), 0.9μL; Reverse primer (10μM), 0.9μL; Taq polymerase (5 U/μL), 0.15μL; DNA (200 ng/μL), 1.0μL; ddH2O , 17.5μL.3. Amplified system of Valsa mali based on ISJ was established for the first time: 10×Reaction Buffer,2.5μL; MgCl2(25 mM),1.5μL; dNTPs(10 mM),0.5μL; Primer (10μM),0.5μL; Taq polymerase (5 U/μL),0.3μL; DNA(200 ng/μL),1.0μL; ddH2O ,18.2μL.4. Genetic diversity of 122 Valsa mali strains from 8 provinces was analyzed using 8 pairs of SRAP primers with high polymorphism and stability. 56 polymorphic bands were amplified, accounting for 75.68% of the total.5. Genetic diversity of 24 Valsa mali strains from diffeent areas in China was analyzed by 6 ISJ primers with high polymorphism and stability. 41 polymorphic bands were amplified, accounting for 66.13% of the total, and the polymorphism was not accordant with geographic origins.6. Genetic polymorphism of 122 Valsa mali strains collected from different regions of China was analyzed with SRAP. The result indicates that there is a good correlation between SRAP clustering result and the geographic origins of the strains. The pathogenicity difference and SRAP polymorphism were also compared. The result shows that good correlection exsists between the SRAP clustering outcome and pathogenicity difference.