The Effcts Of High Temperature On Pathogenicity Of Botrysphaeria Dothidea

Apple ring rot is a disease that damages apple fruit and branches,which is the main disease of apple in China.Apple ring rot is caused by two major pathogens: B.dothidea and B.kuwatsukai.Previous studies in our laboratory found that the adaptability of the two pathogens to temperature was quite different.B.dothidea has the ability to grow at high temperatures.In this paper,the effects of high temperature on the pathogenicity of B.dothidea and B.kuwatsukai were compared.The following results were obtained:1 Apple fruit were collected in 60 days,90 days,120 days after full bloom,and in harvested period.B.dothidea and B.kuwatsukai were inoculated on apple fruit at 25°C,35°C and 37°C.The results showed that B.dothidea has significantly stronger pathogenicity for different period fruit at 35°C than that at 25°C.To test virulence,apple fruit were inoculated at more temperature scales.The results showed that B.dothidea can cause disease at 20°C~37°C and have highest virulence at 32.5°C.These results show that B.dothidea has high temperature pathogenicity to apple fruit.2 Based on transcriptome differences,a unique gene cluster of B.dothidea was selected.There are 5 genes in the unique gene cluster: shikimate-5-dehydrogenase(BsSDH),shikimate kinase(BsSK),dehydroquinate dehydroatase related(BsDHQ),Fungal specific transcription factor domain(BsFSTF),and pathogenic-related protein Pep2(BsPep2).Among them BsSDH and BsSK are genes related with shikimate pathway.qPCR was used to analyze the expression levels of these genes under culture conditions and diseased fruit.At 35°C in media all 5 genes expression levels increased first and then decreased with time.The expression of BsSDH was highest at 12 h,BsDHQ,BsSK,BsFSTF,and BsPep2 were at 6 h.At 35°C on diseased fruit,there were differences in expression levels to 5 genes.The expression level of BsSDH and BsDHQ did not change significantly,BsSK,Bs FSTF and BsPep2 increased first and then decreased with time,and the expression were highest at 24 h.These results indicated that the gene cluster was associated with pathogenicity of B.dothidea in apple plants under high temperature.3 Rootstock seedlings were inoculated with B.dothidea and B.kuwatsukairespectively,then treated with drounght stress.The results showed thatboth two pathogens could cause necrotic lesions,or canker on the trunck.B.dothidea was thought to cause trunck canker under drounght stress.Our results showed that B.kuwatsukai was the potencial to lead to canker on apple trunck under drought stress.In summary,this study discovered that B.dothidea had thestronger virulence to apple fruit at high temperatures.