Identification, Biological Characteristics And Infection Process Of Colletotrichum Gloeosporioides And Fungicide Selection

The yam anthracnose is an important disease .In 1999,the percentage of diseased plant reached 100% and the output reduced 90-100% in Ya'an City, Sichuan Province . The symptom characteristics of the anthracnose on the disease leaf and stem were reported. According to the morphological characteristics and size of the acervulus , conidiophore and condium, the pathogen was identified as Colletotrichum gloeosporioides Penz.The best medium for the mycelia growth and spores formation was PYA. The optimum temperature and pH for the mycelia growth and spores formation were 25℃ and 7,respectively.The fluorescence promoted the spore formation while the blacklight inhibited it . Among carbohydrate which the pathogen could be utilized, the best carbon sources was malt sugar while the worst one was lactose . Organic nitrogen was better than inorganic nitrogen for mycelial growth and spore formation . Yeast extract was the best nitrogen source while the worst one was KNO3. The optimum temperature and relative humidity (RH) for spore germination were 20 - 30 ℃ ,70 -100%,respectively,but the spore formation condition was best in drops of water .The spore couldn't germinate at lower than 60% RH. The optimum pH was 4-6.The spore couldn't germinate at pH higher than 8. The light was favorable for the spore germination.The spores overwintered on axillary bud, leaf and stem .The conidia were disseminated by airflow The conidia germinate and produce germ tube and penetrate through direct penetration, and the hypha penetrate through stoma. At 25 ℃,the pathogen need 18h to complete the infection process .At 25 ℃ and 30℃ , the incubation period are 3-6d.and 4-7d., respectively. The incubation period is 6-7d under natural condition (24.5℃) of Ya'an.