Preliminary Study On The Anthracnose Of Tripterygium Wilfordii

In recent years, it has accelerated the development and utilization on the medicinal value of the Tripterygium wilfordii. The vegetative cycle of Tripterygium wilfordii's root is very long and its leaves which can be used must live on the above 6-year-old plants, therefore, the wild Tripterygium wilfordii are not enough to meet human's needs. In order to satisfy the human's demand, the local people have planted a large area of Tripterygium wilfordii pure stands in Taining country. With the appearance of the large-area planted forest, the diseases (such as powdery mildew, anthracnose, and angular leaf spot) are rampant, too. The anthracnose is so serious that the leaves' effective component is reduced greatly. Moreover, a lot of leaves are defoliated ahead of time, which causes a big economic loss to the local people. Simultaneously, because of our lack of the knowledge of the occurrence characteristics and development of Tripterygium wilfordii anthracnose in our province, the prevention is restricted. Therefore, we have made the systematic study on the identification and biological characteristics of the disease, the rule of the occurrence and development, the space distribution style of diseased plant, the Chinese herb extracts inhibiting of the disease, the indoor toxicities of fungicides of the disease and so on. The result is as follows:1. Symptom of the Tripterygium wilfordii anthracnoseThe Tripterygium wilfordii anthracnose mainly did harms to Tripterygium wilfordii leaves. In the initial period, the leaves appeared some celadon circle scabs. Then, the scabs expanded to be brown ovals with some little black dots, which sunken and split crack. The concentric ring scabs length was 10-20 mm, width 7-12 mm. In the high humidity, there were several orange dots on the scabs. Those were piles of conidia of the pathogen.2. Identification and biological characteristics of the pathogenThe pathogen of the Tripterygium wilfordii anthracnose was proved to be Colletotrichum gloeosporioides (Penz.) Sacc.. The hypha grew well on PDA. The optimum temperature was 25℃and the most suitable pH was 6. To the carbon and nitrogen nutrition, the carbon nutrition was the most advantageous to the hypha's growth, and the nitrogen nutrition was the most advantageous to the conidia generation. The hypha used the carbon nutrition more strongly than the nitrogen nutrition. Conidia germinated quickly in the appropriate temperature. They began to germinate after 4 hours, and the germination rate could reach 98.6% after 6 hours. The conidia could germinate one appressoria from the one ends' cells. The optimum temperature for conidia germination was 25℃. The optimum pH was 7. Conidia could reach a response high germination rate if the humidity was more than 95 percent and sufficient light. The conidia responded insensitively to light and its lethal condition is 51℃at 10 min.3. The rule of the occurrence and development of the Tripterygium wilfordii anthracnoseThe Tripterygium wilfordii anthracnose was a kind of disease under the condition of high temperature and high humidity. The pathogen survived in winter on the defoliation or invalid body in the form of hyphae. The pathogen invaded the plants at the first ten days of May, aggravated by the temperature, and the incubation period was 3-5 days. At the middle ten days of May, the disease invaded new treetop, and then extended to the whole tree. The disease was outbreak from June to August, alleviated in September and stopped developing in November. The pathogen invaded the Tripterygium wilfordii mainly by conidia through rain and wind. The site condition and the stand structure had a remarkable impact on the disease's occurrence and development.4. Spatial distribution of diseased plantsThe result of congregation indexed and analysis of Iwao's regression and Taylor's exponential law model indicated identically that the spatial distributing type of the diseased plants of Tripterygium wilfordii anthracnose was the aggregated distribution.5. The Chinese herb extracts inhibiting of the diseaseThe inhibition on the pathogen of extracts from 22 kinds of Chinese herbs was researched. It is showed that the extracts of Thinleaf Milkwort Root-bark (Polygala tenuifolia Willd.),Common Anemarrhena Rhizome (Anemarrhena asphodeloides Bunge.),Garden Burnet (Sanguisorba officinalis Linn.),Lightyellow Sophora Root (Sophora flavescens Ait.) and Calamintha chinensis Benth (Gentiana manshurica Kitag.) can inhibit the growth of Tripterygium wilfordii anthracnose, which the inhibition rate is higher than 60%. Especially the inhibition rate to Thinleaf Milkwort Root-bark is 93.15%; the extract of Common Anemarrhena Rhizome was 89.4%. Some of them were lower than 50%,even some still can promote the growth. With the lower concentration, the Chinese herbal extracts's inhibition also reduced.6. The indoor toxicities of fungicides of the diseaseThe results of the study on the fungicides by inhibiting conidia germination showed that, eight kinds of fungicides except Bellkute,Thiram-thiophanate- methyl,Carbendazim and Score were efficient to inhibit the conidia germination. Bellkute had the best inhibition effects, all of which were above 90 percent, Thiram-thiophanate- methyl followed by. Through the regression equation of toxicity and results of EC50, we could find that, Bellkute and Thiram-thiophanate- methyl were efficient to the conidia in sensitivity and virulence. In the study of fungicides' impact on the hypha growth, eight kinds of fungicides except Dithane M-45,Amistar and Armure, others had strongly inhibitory effects. Particularly, the inhibition rates of Bellkute and Thiram-thiophanate- methyl were very high, all higher than 70%. According to the sensitivity, the results were as follows:Systhane>Carbendazim>Bellkute>Thiophanate-methyl>Dithane M-45> Score>Armure>Amistar; According to the toxicity, the result was as follows:Thiophanate-methyl> Score >Bellkute>Armure>Carbendazim> Systhane> Dithane M-45> Amistar. Bellkute and Thiram-thiophanate-methyl had better results in the sensitivity and virulence on the hypha growth.