Studies On Physiological And Biochemical Characteristics Of Colletotrichum Lilii And Screening Of Effectual Fungicides

Lily anthracnose is an important disease in Huoshan County,Anhui Province.In 2005,this disease made lily nearly no production and it badly prevented the llily cultivation in this area.The symptom characteristics of lily anthracnose on the diseased leaf and stem were reported and the causal organism of the anthracnose was identified in this paper.The effects of temperature,pH and nutritional material on mycelial growth and conidial production of the fungus were studied,and the dynamic activity of resistant enzymes in the lily plants inoculated with C.lili were measured.Moreover,EC₅₀values of 7 kinds of fungicides and the co-toxicity of their mixed preparations to the pathogenic fungus were tested by means of colony growth rate method under the condition of laboratory,respectively,to screen the effective mixed preparations for the control of the disease.The test results were as follows.1.The test and microscopical observation showed that the size of conidiophore is 17.94～19.24×3.4～4.0μm and the diameter was 7.02～7.8μm.According to the morphological characteristics and size of the conidiophore,the pathogen was identified as Colletotrichum lilii Plakidas.2.The research of biological characteristics of C.lilii showed that the mycelial could grow at 5-35℃,with the optimum temperature being in the range of 25-30℃.It couldn't grow below5℃or above 40℃.The lethal temperature of conidial was 54℃for 10 min.The mycelium could grow under the condition of pH 3 to 12,showing double peak curve,suggesting that there were two optimum pH values,6.0 and 8.0.The optimum pH for conidial production is between 5.0 and 8.0.The pathogen could use many carbohydrates and nitrogen sources.For mycelial growth on solid media,the optimum carbon source was maltose,sucrose and soluble starch being next,and the worst carbon source was lactose.The optimum medium for conidial production was the one used maltose as carbon source.The suitable carbon sources for mycelial growth in liquid medium(mycelial dry weight)were sucrose and maltose.And the optimum nitrogen source,for mycelial growth,was peptone, CO(NH₂)₂ and NaNO₃ being next.(NH₄)₂SO₄ is the worst one.The medium using CO(NH₂)₂ as nitrogen source is optimum for conidial production.The test of C.lilii grew in liquid medium showed that NH₄NO₃,as a sources of nitrogen,was optimum for mycelial growth.Organic nitrogen was better than inorganic one for mycelial growth and spore production of C.lilii. 3.The activities of PPO,SOD and POD in the lily plants being induced by C.lilii were tested and analyzed respectively in 12 days.The results indicated that PPO and POD enzymes activities in leaves mounted up obviously,which suggested they were disease-resistant enzymes against the C.lilii in lily plant.SOD enzyme activity was improved,which was not significant.4.Under the condition of laboratory,EC₅₀of 7 kinds of fungicides and the co-toxicity of three mixed preparations against C.lilii were tested by means of mycelial growth rate method,respectively.The results showed that EC₅₀of difenoconazole, carbendazin and prochloraz,were 0.04,0.05 and 0.15 mg/L,respectively,suggesting that this three kinds of fungicides all had a good inhibition against the fungus.On the contrary,mancozeb,azoxystrobin,triadimefon,chlorothalonil had higher Ee₅₀value, not suiting for controlling of lily anthracnose.On the basis of preliminary experiments, CTC of the mixtures of the three fungicides were tested,and the results-indicated that the mixture of difenoconazole,carbendazin and prochloraz had no significantly additive effect.