Biological Characteristics Of Colletotrichum Gloeosporioides And Screening Effective Fungicides To Control Dangshan Pear Anthracnose

In recent years, Due to the unfavorable influence of various factors which include unpleasant change of climate, the continually accumulated pathogen, extensive cultivation and management and unscientific disease and insect prevention etc. The pear anthracnose which was lack of enough study, has become the main fungus disease of pear tree in and its surrounding area, which seriously threaten the production of pear. According to the molecular biological identification of anthracnose pathogen isolated from Dangshan County, the biological characteristics were amply studied, and the inhibitory effect of6fungicides and their compounded agents on pear anthracnose pathogen by means of detecting mycelium growth and spore germination, and the control effect on the disease was also tested. In addition, the inhibitory effect of Nanometer Silicon on pear anthracnose pathogen and the synergistic action between Nano-Si and fungicides were also evaluated by measuring the disease development in vivo. The main results were summarized as follows:1. The rDNA sequence of pear anthracnose pathogen （Cg） was determined. Sequence comparing of ITS of Colletotrichum was conducted and a phylogenetic tree based on alignment of their ITS nucleotide sequences was constructed. The results showed that Cg shared the highest sequence similarity （99.0¹00%） with Colletotrichum gloeosporioides. It was confirmed that pear anthracnose pathogen belong to C. gloeosporioides.2. Biological characteristics of C. gloeosporioides were studied. The results showed that the growth temperature ranged from10℃to35℃, with the optimum at28℃. The optimum temperature for conidial germination and germ tube elongation was within20℃to30℃, with the optimum at25℃for the germination and28℃for the elongation. The lethal temperature for conidial germination was49℃for10minutes. There was a wider scope of acidity for mycelia growth and conidia germination. The mycelium could grow well at the pH value from4to11, with the optimum at6.7. The percentage of conidia germination wasn’t significantly different at the pH value ranged from5to9. And the conidia germination was the best when the pH value ranged from6⁷. The utilization effects of different carbon sources and nitrogen sources on "suli" pear anthracnose pathogen were different. In carbon source, colony diameters in d-mannose, maltose and fructose were longer than that of any others, and glucose and sucrose were in second place, The worst carbon source was lactose and propanetriol. The pear anthracnose pathogen could utilize various categories of nitrogen sources efficiently, which included NO₃^-and several kinds of amino acids except L-cysteine. The worst nitrogen source was NH₄^-. Moreover, the NH₄^-could inhibit the mycelia growth of the pear anthracnose pathogen.3. Effective Fungicides was screened by means of mycelium growth and spore germination method, the control effect to the disease by fruit inoculation methods was also tested. The results indicated that the six fungicides inhibited the growth of C. Gloeosporioides, but the mode and the stage of different fungicides were different. The inhibitory effect of prochloraz-manganese chloride complex on the hypha growth was the best with the EC₅₀ of0.096μg mL^-1, and the following was propiconazol, flusilazole, azoxystrobin, difenoconazole and carbendazim respectively. Azoxystrobin showed the greatest inhibition on the spore germination and germ tube elongation, whose EC₅₀ was3.4119,0.1621μg mL^-1 respectively. However, propiconazol presented poor inhibition, with the conidial germination rate up95.52%and the germ tube length up96.26μm. The optimum ration of prochloraz-manganese chloride complex and difenoconazole was C:B and A:D, the combined toxicity coefficients （CTC） were both more than120the CTC was769.81of the optimum ration at m:n of the X and Y with the EC50of0.0101μg mL^-1, which showed strong synergistic actions all above. However, the CTC of the mixtures of prochloraz-manganese chloride complex and flusilazole was below100, which presented antagonism effect.The results of the vitro test indicated that: The control effect were both100%by soaking500dilution times of prochloraz-manganese chloride complex and X·Y（m:n）. Azoxystrobin and Pr-Mn+difenoconazole showed lower control effect, which were38.76%and43.57%, respectively. The lowest control effect was16.89%of propiconazol. Inhibitory effect with different ways of agent applications showed significant differences. The control effect by fungicides application after inoculation was obviously better than by inoculation after fungicides application. Apply two ways of sprayer and soak to compare that the control effect by soaking was obviously higher than by spraying of the same agent, especially at low concentrations.4. Effect of nano silicon against anthrancnose of pear caused by C. gloeosporioides was studied. The result showed that there were no inhibitory effects on hypha growth, spore germination and germ tube elongation of C. gloeosporioides treated with different concentrations of nano-silicon. But it showed control effect on the disease spot’s expansion with the efficiency was up to30.45%by the treatment which soaked by100dilution times nano-silicon solution. nano-silicon prevention and control the pear anthracnose in field was also tested, and the results showed that nano-silicon could control pear anthracnose. And the disease fruit rate was controlled within13.6%and the efficiency was36.5%used by200mM nano-silicon preparations.The synergistic action between nano-silicon and fungicides was studied on mycelium growth and spore germination, and the results indicated addition or synergy. The optimun ration of Pr-Mn+difenoconazole and nano-silicon was at B:A with the CTC was312.91the CTC was260.28of the optimum ration at C:A of the mix of nano silicon and X Y（m:n）, the CTC were all higher than100of the different ration of the mix of nano silicon and prochloraz-manganese chloride complex. The synergistic of Nano-Si and fungicides was influenced by factors of fungicides, combination, experimental method and etc. in vivo.