Genetic Diversity Of Venturia Inaequalis With SSR Markers

Apple scab, caused by Venturia inaequalis (Cooke) Wint., is one of the most serious diseases of apple and ornamental crabapple. Both leaves and fruits can be infected. Infected leaves may drop early resulting in weakening trees, with poor fruit production. Infected fruits are blemished and often severely deformed. In China, apple scab, which limitis to only occur in a few local sites, is pointed as quarantine objective, but in recent years, this disease is expanding to larger areas and severely threatening to apple industry in China. It was a new disease founded firstly in 1997 in Xinping, Liquan, Yangling, and Xunyi in Shaanxi province. The main results obtained by molecular analysis with SSR thchnique are as follows: 1. The genomic DNA of Venturia inaequalis of apple was extracted by useing Squash-Blot method, which can reduce the harm of toxicity to experimenters, chemical reagents and need inexpensive apparatus. The main advantage of this technique can greatly speed up experiment and is simple and easy to operation. Many samples can be crushed onto a single membrane piece, and a single operator can analyse hundreds of samples in one day. It can greatly cut short of the time of extracting genomic DNA from Venturia inaequalis of apple. Usually, the conventional method took more than one month to extract genomic DNA from mycelium grown in culture medium, but by using this method only took several days. 2. We have set up the optimizing SSR reaction system of Venturia inaequalis:each 25 μL amplification reaction solution was comprised 10×Buffer(MgCl2 20 mmol/L)2.5 μL, dNTP100 μmol/L, primers 0.5 μmol/L, Taq DNA polymerase 1.5 U, template DNA 2 mg/L, ddH2O19.5 μL。Amplication program is:2 min at 93℃, 30 s at 57℃:then 40 cycles that consisted of 1 min at 72℃, 30 s at 93℃, 30 s at 57℃; followed by 10min extension at 72℃. The result of PCR amplification showed that the PCR system had good repeat and stability. 3. We have analyzed the genetic diversity of 160 isolates origined from UK, India and Shannxi province of China. Results showed that isolates origined from China, UK and most of isolates origined from India had close relationship, but some India's isolates-RD1, G1-10, R1-1, G2-8, G1-2 and R1-12 varied in some dgree, and there were no relationship with those from Shannxi province of China and UK. Results also indicated that there was no relatetionship between the geographic distance and differnet apple cultivars. This study can help us to have better understand what the genetic diversity of Venturia inaequalis of apple is and how to control this disease (choosing resistant variety, reduce the virulent variation) by fowllowing our research result.