Study On The Incedence Of Anthracnose On Litchi Chinese Sonn, And It's Pathogen

Investigations in the field showed that the incidence of disease had two increasing peaks. One was in the last ten days of April through to May; the other in the last ten days of May through to June. This was identified with the incidence of tender leaves. In the field it was seen that different varieties of Litchi chinensis Sonn exhibited different disease grades. Feizixiao and Baitangyin et al were more serious relatively than Lingshanxiangli, Sanyuehong and Heli.Base on the morphological characters and the results of internal transcribed spaces (ITS) sequence data, the pathogen was identified as Colletotrichum gloeosporioides.Five isolates of C. gloeosporioides isolated from the leaves of Litchi chinensis Sonn which was named according with the name of the placename showed different pathogenicities when inoculated on Feizixiao. In vitro inoculation showed that Feizixiao was the most seriouest one among the five tested varieties. The study also showed that the culture filtrate of the pathogen exhibitied phytotoxicity to the host leaves. The phytotoxicity of the culture filtrate remained even after heat treatment (121 C, 25min).RAPD analysis of five C. gloeosporioides isolates and one isolate from aniseed were compared. Polymorphic RAPD bands were obtained with threeprimers (s33, s97, s104). Dendrogram generated by NJTREE divided all isolates into two groups. Cluster analysis showed that the difference among isolates related to the host plants and the pathogenicity.Effect of temperature, pH, light, carbon source and moisture on the mycelial growth, sporulation and conidial germination of NN isolate was investigated. For the mycelial growth, the range of temperature was 10~40 C,the optimum being 28 C,and the range of pH was 3.5~10.5, the optimum being range 5~6.5.For the sporulation, the range of temperature was 10~40癈,and the optimum being 25"C, and the range of pH was 3.5~10.5, the optimum being 4~4.5. For the conidial germination, the range of temperature was 10~40"C;the optimum being 25~28C,and the range of pH was 3.5~10.5, the optimum being 6.5. The treatment of darkness or continuous fluorescent light or with 12h alternative fluorescent did not show significant effect on the mycelial growth, but 12h alternative fluorescent could promote sporulation.When in water or the relative humidity reached 100%, the percentage of conidial germination was the highest among the treatments.It was also recorded that the glucose, sucrose, maltose or fructose could promote the conidial germination.In vitro examination indicated that Sportak showing the most strongest control effects among the ten tested fungicides.