Studies On Anthracnose Of Radix Curcumae

Radix Curcumae is an important medicinal plant. The root tuber of four Curcuma species:Curcuma wenyujin Y. H. Chen et C. Ling, C. longa L., C. kwangsiensis S. G. Lee et C. F. Liang and C. phaeocaulis Valeton, can be used as Radix Curcumae. Colletotrichum capsici (sfd.) is a new and destructive disease in main production zone of Radix Curcumae. Symptoms of the disease, isolation and identification of the pathogen, biological characteristics, infection and indoor fungicides screening were reported in this paper. It was studied systematically. The main results were as follows:1. Symptoms of Colletotrichum capsici and the pathogen identificationIn the early stages of the disease occurs, leaf blade showed small pale brown diseased spots, which may develop into orbicular or nearly orbicular ones of uniform size. The edge of the spots formed ring circles and the colour was dark brown, while the inner colour of spots was pale white. Some spots were surrounded by discolored halo. As the development of the disease, many disease spots joined and numerous small black dot (stroma) scattered on the surface of lesions especially in the rainy day.Based on the morphological classification and molecular biology technology, the pathogen belongs to Colletotrichum capsici (sfd.). Acervulus with brown bristles was round or nearly round, which scattered or gathered under the host’s epiderm at the beginning, and broke through the host’s epiderm later. Conidia, nonseptate, colorless, falciform, is in size of21.11～24.91μm×2.31～4.34μm. Appressorium was dark brown and nearly round or irregular.2. The biological characteristics of Colletotrichum capsici.Results showed that:the temperature range for hyphae growth was10～35℃, the optimum was25℃. And for sporulating, the temperature range was20～35℃, the optimum was30℃. The pathogen could grow better on20%leaves’ juice+PDA than the others. The best medium for sporulating was also20%leaves’ juice+PDA. pH value range for hyphae’s growth and sporulate was4-10, the optimum for hypha’s growth was6～7, and the optimum for sporulating was6. In the utilization of carbon sources, glucose was the best for hyphae’s growth, and the most suitable nitrogen source was peptone. Light had a little influence on sopeulating, but the light/dark pattern was good for hyphae’s growth.The temperature range for germination of conidia was between15and35℃, and the optimal temperature was30℃. After2.5h, the conidia started to germinate. And the ways of germination were various. Conidia has no strict nutritional requirements for germination. But the conidia did not germinate until the RH was above95%. Light was neither inhibitory nor stimulatory to germination. The lethal temperature of conidia was54℃1Omin.3. The infection conditions of Colletotrichum capsici.After inoculation, conidia of Colletotrichum capsici began to germinate within four hours. Then, after24hours, the pathogen started to penetrate into host through three paths.①Stomata,②Between cells,③Direct infect。4. Virulence determination of fungicides to the pathogenThe five fungicides were tested in laboratory to determine the effect on growth of mycelium. The results showed that five fungicides had inhibition on the growth of mycelium. Carbendazim and prochloraz were the most effective ones. Difenoconazole was inferior to them and triadimefon was the worst one.