Detection of powdery mikiew fungus from winter buds by the polymerase chai* reaction using species-specifrc prinerset.

白粉病真菌一般靠闭锁毛虫越冬。另一方面，众所周知，紫薇（Lagerstroemia indica）的白粉病真菌在植物的冬芽中越冬。如果能够检测到潜伏侵染冬芽的真菌，就可以通过冬芽侵染频率获得冬芽侵染时间的信息。这可能会澄清这种真菌的生命周期，从而导致疾病预测的可能性。为此，我们尝试采用聚合酶链反应方法，建立了紫薇冬蕾白粉病的检测方法。结果如下：1)测定了各种白粉病真菌的ITS区（包括5.8S rDNA）DNA序列，并以此序列构建了4条针对紫薇白粉病真菌（Erysiphe australiana）的特异性引物。2)该特异性引物集只扩增了紫薇白粉病的DNA。3)用该引物对紫薇叶片真菌分离物进行PCR扩增时，检测到一些微弱的条带。4)利用限制性内切酶Xhol I进行PCR-RFLP可用于区分紫薇白粉病和真菌分离物。5)引物组SA2/SA3对紫薇真菌的最低检出限为0.0025pg DNA; 6)采用Dneasy Plant Mini- Kit结合Hepese清洗技术，成功提取了紫薇叶片中的DNA。

Powdery mildew fungi generally overwinter by cleistothecla. On the other hand, the powdery mildew fungus of crape myrtle (Lagerstroemia indica) is known to overwinter in winter buds of the plant. If the fungus latently infecting the winter buds can be detected, we can obtain the information as to when the winter buds are infected with infection frequency of the winter buds. This may clarify the life cycle of this fungus, which leads to the possibility of disease forecasting. We thus tried to develop the detection method of powdery mildew from the winter buds of crape myrtle by the polymerase chain reaction using species-specific primer set. The results are as follows.1)DNA sequences of the ITS regions including 5.8S rDNA were determined for various powdery mildew fungi Based on the sequences, four primers specific to the powdery mildew fungus (Erysiphe australiana) of crape myrtle were constructed 2) Only the DNA of the powdery mildew of crape myrtle was amplified by the specific primer set, which indicates the usefulness of the primer set 3) Some faint bands were detected when fungal isolates from leaves of crape myrtle were subjected to the PCR amplification using the specific primer set. Some of these bands could not be removed even if the annealing temperature was changed 4)PCR-RFLP using the restriction enzyme Xhol I was useful to differentiate foe crape myrtle powdery mildew from the fungal isolates. 5) The minimum limit of detection the primer set SA2/SA3 was 0.0025pg DNA for the crape myrtle fungus, 6) Danas successfully extracted from the leaves of crape myrtle by using Dneasy Plant Mini- Kit combined with cleaning by Hepese.