金丝桃叶尖焦枯病病原初步研究

从江西农业大学校园内发生金丝桃叶尖焦枯病的病株中，随机采集50片病叶按常规方法分别进行组织分离培养，结果有46片病叶未分离到病菌，4片分离到葡萄孢属(Botrytis)、链格孢属(Alternaria)或曲霉属(Aspergillus)真菌。同时，另取50片相同症状的新鲜金丝桃叶尖焦枯病病叶进行保湿培养，观察病征产生情况，结果绝大多数病叶未有病征产生。病害调查发现，不同生境条件下金丝桃叶尖焦枯病发生轻重显著不同，空旷地阳光直射处金丝桃叶尖焦枯病病叶率为61．3％，病情指数为38．9；而生长于树荫底下无阳光直射处金丝桃叶尖焦枯病病叶率为18．4％，病情指数为9．5。综合上述实验结果认为，发生于江西农业大学校园内的金丝桃叶尖焦枯病不是一种由病原物引起的侵染性病害，而可能是由阳光照射引起。

Preliminary Studies on the Pathogen of Hypericum monogynum Leaf Blight

Fifty samples diseased with Hypericum monogynum leaf blight were collected at random from the campus of Jiangxi Agricultural University. These samples were cultured on PDA culture medium in a standard way. Three kinds of fungi were isolated from only four leaf samples and they belong to the genus of Botrytis, Alternaria, and Aspergillus, respectively. Another fifty diseased leaf samples were cultured under wet conditions at the same time, but no causal organism was observed. Occurrence of Hypericum monogynum leaf blight was investigated in August, 2004. Both disease incidence and disease index were closely related to the living conditions of Hyperioum monogynum. In sunshine, the disease incidence and disease index were 61.3% and 38.9, significantly higher than those in shadow with 18.4% and 9.5. These results showed that the Hypericum monogynum leaf blight occurred on the campus of Jiangxi Agricultural University was not a kind of infected disease, but probably caused by sunlight.