Pathogen Diversity Of Marssonina Blotch And Apple Variety Resistance Identification To Marssonina Coronaria

Marssonina leaf blotch caused by Marssonina coronaria, is the main disease causing premature defoliation of apples. It occures in most apple production areas in China. In recent years, with the development of bagging, growers pay a little attention to leaf diseases, so the disease is becoming more and more serious. It causes apple tree potential receding yield decrease and quality decline.The symptoms of the apple marssonina blotch are very complecated.Different symptom can be found even on same trees. Their genetic diversity was analised by SSR plolymorphic cluster.On the other hand, the resistances of about 85 apple materials to Marssonina leaf blotch were avaluated in order to understant the resistance levels of mostly planted cultivars and potential germplasm resources. The results were as follows:(1) The symptoms were divided into four types through SSR clustering analysis: A. Dark brown spot . B.Yellowish defoliation . C. Shoot leaf spot. D. Brown spot.(2) Polygene sequence (ITS,β-tubulin1,EF1,α-action,calmodulin ) comparions showed that isolates had genetic variation in each gene, but phylogenetics analysis showed that variation in gene positions had no coordination with with symptom types. So, we suppose that the basepair changes and sympotom diversity belong to the intraspecies variations, and the pathogen of apple Marrsonia blotch should be stricted in is in a single specie.(3) Eighty-five apple materials (cultivars, selections or strains) resistances were identified through artificial inoculation in plastic boxes and investigation in fields. The results showed that highest susceptibale materials included 17 cultivars, such as"NY463","Jonathan", accounting for 20% of tested materials, susceptible materials 36 cultivars including"Fuji',"Pink lady","Qinyang", etc, accounting for 42.4%, 19 cultivars including"Pinova","Granny Smith", etc, were moderately resistant, accounting for 22.4%, Resistant disease cultivars were"Jiguen","GalaⅡ",etc, 6 cultivars, accounting for 7.1% of the tested materials, The cultivars"Yanfeng","Shanxia","Wojin","Dongguang","Huanxi","Yanguang","Zaojie", were highest resistant. There was no immune material found.