| Rape is an important oil plants in China. Sclerotinia stem rot causing by Sclerotinia sclerotiorum (Lib.) de Bary lead to large loss to the yield of rapeseed. Science S. sclerotiorum has far-ranging geographic distribution and host origin, many scholars have different ideas in its pathogenicity .As our important rapeseed producing area, Shannxi has unique geographical environment. The Sclerotinia stem rot is seriously in southern part of Shannxi, the middle part is lighter. However, there is scarce of study and report about the pathogenicity of and its population distribution. To determine the relationship between pathogenicity of and its geographic distribution and host origin and its group structure, and the macrography distribution of S. sclerotiorum to provide the scientific base for disease controlling, two thousands and ten sclerotia samples from fifteen different regions and hosts in Shannxi province were collected ,isolated in 2008-2009.860 isolates were sclerected to test pathogenicity and mycelial compatibility groups ,the results of the research showed as follows:1,Both toothpick inoculation on stem and directly putting fungi disc on deteched leaf were used for 40 random selecting isolates to inoculate rape. The results shows that the trend of the lesions diameter formed by two inoculation have no difference.But it is easier and simpler to get deteched leaves ,and to handle the method,and 48h after inoculation can survey the lesions, so the method of directly putting fungi disc on deteched leaves is fit to pathogenicity test for large number isolates.2,Eight hundreds and sixty isolates of Sclerotinia sclerotiorum isolated from nape and other five hosts(sunflower,leonurus,platycodon grandiflorum,lettuce,cabbage) in different regions of Shannxi Province were tested for pathogenicity by directly putting mycelium-infested agar plug on rape leaf. The results showed that all isolates of S.sclerotiorum tested could infect the oilseed rape leaf and form a lesion except two isolates from Mianxian and Chenggu. Th smallest average lesions diameter is 0.5mm, and the largest is 42.6mm. The isolates with different pathogenicity were found in each area and even one field, and the analysis of variance shows difference significant. Isolates from other hosts could cause disease on the deteached oilseed rape leaves. These differences suggested that the different isolates of S. sclerotiorum had differences in pathogenicity and the pathogenicity might not be related to geographic distribution and host origin3 Sixteen isolates from six hosts were inoculated to five common hosts (Brassica napus ,Helianthus annuus,Lactuca sativa,Brassica rapa.chinensis,Glycine max) by deteched leaves and live organs to determine the pathogenicity of the S. sclerotiorum.The results shows that except one isolate from Brassica napus other isolates could infect all five hosts.The lesions diameter were obviously different.The analysis of variance showed that the isolates pathogenicity are different on the different hosts and the pathogenicity not be related to host origin . The pathogenicity of S. sclerotiorum to its collecting host may not the most serious ,it can shows more serious pathogenicity to other host.4 Two hundreds and sixity-five isolates were paried on PDA medium to determine the mycelial compatibility groups,the results showed there were 125 completely compatibility groups, 245 localized compatibility groups and 694 incompatibility groups.The majority of the isolates of completely compatibility groups comes from the same geographic distribution,but there also some isolates from differents regions, and the completely compatibility groups include different pathogenicity isolates. All the results showed that the isolates mycelial compatibility groups from Shannxi is complexity,and the mycelial compatibility not related to the geographic distribution and pathogenicity.
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