Biological Characteristics And Effective Fungicide Selection Of Anthracnose Pathogen Of Ophiopogon Japonicus

Two pathogenic fungus causing Ophiopogon japonicus anthracnose were isolated and identified.The biological characteristics of anthracnose pathogen of Ophiopogon japonicus and the activity of cell wall degrading enzymes(CWDE) were studied.The toxicity of five kinds of fungicides and their mixed preparations to the anthracnose pathogen of Ophiopogon japonicus were tested.Moreover the inhibition effect of Bacillus subtitles to the anthracnose pathogen of Ophiopogon japonicus was studied.The main results were summarized as follows:1.Identification of the anthracnose pathogen of Ophiopogon japonicusAccording to the results of mensuration which was about field symptom, characteristics of morphology,culture and the classification criteria of Colletotrichum edited by Sutton,the anthracnose pathogen of Ophiopogon japonicus in hefei city of Anhui province was identified as Colletotrichum dematium and Colletotrichum gloeosporioides.2.Biological characteristics of anthracnose pathogen of Ophiopogon japonicusThe effects of temperature,pH,light and nutriment on the mycelial growth,conidial production and spore germination were studied by means of decussating method, hemocytometer measurement method and concave slides method.The results showed that the optimum temperature for the mycelial growth of C.dematium and C.gloeosporioides were 25℃and 28℃,respectively,and the lethal temperature of conidial was 50℃and 55℃10 min,respectively.And the sporulation of theirs obtained maximum at 28℃.The optimum temperature for spore germination of theirs were 25℃and 28℃,respectively.The optimum pH value for mycelium growth of C.dematium and C.gloeosporioides was pH8 and pH6 severally.The optimum pH value for sporulation was pH4.The lights had no infulence to the anthracnose pathogen of Ophiopogon japonicus.The optimum carbon sources for mycelium growth of C.dematium was maltose and for sporulation was starch.Fructose and glucose were the optimum carbon sources for mycelium growth of C.gloeosporioides and sorbose was suitable for sporulation.The optimum nitrogen sources for mycelium growth were beef extract and protein peptone.Yeast extract could promote C.gloeosporioides to sporulate.3.Activity of the Cell wall degradation enzymes(CWDE) produced by anthracnose pathogen of Ophiopogon japonicusActivity of the CWDE(Cx and PMG) which produced by anthracnose pathogen of Ophiopogon japonicus on different cultural conditions and in different parts of the diseased leaf were tested by the method of DNS and coomassie brilliant blue G250.The results showed that the activity of CWDE produced by C.dematium reached peak value at 6^th day or 25℃,and the optimum pH value for Cx and PMG was 8 and 7 respectively.As for C. gloeosporioides,the activity of CWDE reached peak value at 5^th days,28℃and pH6.There were obvious difference in CWDE activity among three parts of diseased leaves. The CWDE activity in the lesion part was the lowest.The CWDE activity in the healthy part next to the boundary part of the healthy and diseased was higher.The activity of CWDE in the boundary part of the healthy and diseased was the highest.4.Screening of effective fungicides to anthracnose pathogen of Ophiopogon japonicus4.1 Toxicity tests of fungicides to anthracnose pathogen of Ophiopogon japonicusThe inhibition effect of Propiconazole and Azoxystrobin to C.dematium and the Difenoconazole and Propiconazole to C.gloeosporioides were better than the others. Azoxystrobin could inhibit conidium germination effectively.Propiconazole and Azoxystrobin had strong effect to the inhibition percentage of germ tube elongation of C.dematium.The germ tube elongation of C.gloeosporioides was extremely sensitive to Difenoconazole and Propiconazole.The co-toxicity index(CTC) of the mixed fungicides were tested and the results showed that the mixture of Mancozeb and Azoxystrobin had significant additive effect(CTC＞200).The mixture of Mancozeb and Propiconazole had significant antagonism effect(CTC＜50).The best matching ratio of Mancozeb and Azoxystrobin for C.dematium was 3:7,the EC₅₀ was 0.0695μg/ml and the CTC was 397.07.Meanwhile the best matching ratio was 5:5 for C.gloeosporioides,the EC₅₀ was 0.5491μg/ml and the CTC was 305.22.4.2 Inhibition effect of Bacillus subtitles to anthracnose pathogen of Ophiopogon japonicusThe results showed that anthracnose pathogens of Ophiopogon japonicus were inhibited obviously by the cultural solution of Bacillus subtilis.The inhibition percentage of 10-fold and 50-fold dilution of cultural solution of Bacillus subtilis were all 100%.The inhibition percentage of Bacillus subtilis descended with the increase of dilution concentration.And the effect of each teatment of BS80-6 was better than that of the primary Bacillus subtilis.