中文摘要：

对采自中国4个省份的9个梨树腐烂病菌分离株和7个苹果树腐烂病菌分离株的ITS序列进行了测定和分析,并结合GenBank的有性型Valsa ceratosperma、V.ambiens和V.mali的ITS序列构建了系统发育树。结果表明梨和苹果树的各分离株在ITS核苷酸序列上分化较小（p-distance=1.55%）,均在V.ceratosperma聚类组,但二者又分别处于两个独立小分支。其与V.ambiens和V.mali处在不同的聚类组中,且亲缘关系较远,表明供试梨树腐烂病菌并非V.ambiens。培养性状和生物学特点的研究结果还发现,梨树腐烂病菌各分离株无论在菌落颜色、产孢特点、还是37℃高温的生长情况都和苹果腐烂病菌有一定差别。前者菌落始在PDA终为乳白色,而后者菌落初为白色后期变褐色;在20%ABA上,前者形成的产孢体较大而数量较少,在37℃高温下能正常生长,后者则形成的产孢体较小而数量较多,在37℃高温下不能正常生长。并未发现二者在子实体上有稳定明显的差异。因而表明梨树腐烂病菌应为V.ceratosperma,但可用培养性状和生物学特点进行区分其和苹果树腐烂病菌。

英文摘要：

Valsa canker weakens the growth of pear trees and causes economic losses. The species identity of the pathogen of Valsa canker on pear tree was determined through a combined study of rDNA-ITS sequences and cultural characteristics of isolates from apple trees and pear trees in China. Phylogenetic analysis showed that the isolates both from pear trees and apple trees clustered together with the isolates of V. ceratosperma and were distinct from those of V. ambiens. Both pear tree isolates and apple trees isolates formed exclusive clades but with low genetic distance （p-distance =1.55%）. No stable morphological differences were observed among the isolates from different hosts. Nevertheless, some cultural characteristics were obviously different between the isolates from the different hosts. Culturing on the PDA medium, the colony color of the isolates from the pear trees remained milk-white throughout the cultural period, but that of isolates from apple trees changed from white at first to light brown in the later period. On 20% ABA, a few larger conidiomata were produced by the isolates from pear trees, while many smaller conidiomata were produced by apple-tree isolates. At 37℃ the pear-trees isolates developed normally, but the growth of apple-tree isolates ceased. The results showed that the pathogen of pear canker is V. ceratosperma, and it can be distinguished from the apple canker pathogen by some cultural characteristics.