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Pear ring rot, pear black spot and pear anthracnose are three serious diseases in many areas of China, and they can infect fruits and leaves of pear with lots of economic losses. It is important to detect the diseases in the early period and control them effectively. The aim of this study was to build a disease-detected system using molecular technology, screen the effective fungicide, monitor the change of activity of some enzymes associated with resistance by Real-time PCR and control these three diseases in the field with the mixture of antagonistic bacterium and effective fungicide. The results were as follows:The DNA of Colletotrichum gloeosporioides and Botryosphaeria berengeriana were extracted in this paper. Based on the differences of internal transcribed space (ITS) sequences of Colletotrichum genus and Botryosphaeria genus, two pairs of species-specific primers TJ1/TJ2and LW1/LW2were designed and synthesized. Two single specificity PCR bands of317bp and325bp can be amplified from the DNA of C. gloeosporioides and B. berengeriana while other species strains all had no specific band. The sensitivity of Regular PCR and Nested PCR were also tested in this paper. The detection sensitivity was10pg of genomic DNA for Regular PCR, and100ag for Nested PCR, which means that the detection sensitivity can increase10000-fold. The DNA of pear tissue which was sprayed with10/mL conidial suspension of B. berengeriana can be detected by Nested PCR. So the population growth dynamic of the pathogens in orchard can be detected stably and quickly by Nested PCR method.The toxicity to B. berengeriana strain P-16, C. gloeosporioides strain1-1and Alternate alternate A-1were tested with some fungicides. The results showed that25%propiconazole (EC) could inhibit effectively the mycelia growth of A. alternate, B. berengeriana and C. gloeosporioides with EC50value0.031μg/ml,0.019μg/ml and0.020μg/ml. Besides,10%difenoconazole(WP),25%prochloraz(EC),40%flusilazole(EC) and30%hexaconazole(WP) had high toxicity, too. But some fungicides, like50% Dimethomorph(WP),25%Metalaxyl(WP) and15%Triazolone, could not inhibit the mycelia growth of pathogen very well.Biological control can reduce the use of chemical fungicides and the residue on fruit,and it can also protect natural ecological environment. The aim of this study was to control three pear diseases by mixing25%propiconazole (EC) and antagonistic strain sf-628,which could effectively inhibit the mycelia growth of B.berengeriana, C.gloeosporioides and A.alternate in the preliminary studies. The control effects against Pear ring rot was86.2%,86.9%, and64.9%. when treated by the mixture,25%propiconazole (EC), and antagonistic strain sf-628, respectively. The control effects against Pear anthracnose was80.1%,78.8%, and63.0%when treated by the mixture,25%propiconazole (EC), and antagonistic strain sf-628, respectively. The control effects against Pear black spot was83.1%,85.8%, and77.0%when treated by the mixture,25%propiconazole (EC), and antagonistic strain sf-628, respectively. The above results showed that although the mixture treatment involved1/3amount of chemical fungicides compared with fungicides treatment, the control effect of mixture was as same as the chemical fungicide.The results of experiments also showed that there are some effects on the activity change of defense enzymes of pear leaves after inoculated biocontrol bacterium, such as phenylalanine ammonia lyase(PAL) and catalase(CAT). The results of Real-time PCR showed that:the enzyme activities of PAL and CAT can be increased greatly compared with control. The amount of phenylalanine ammonialyase(PAL) and catalase (CAT) was2.4fold and3.5fold compared with control on24h after inoculation, respectively, which means the accumulation of active oxygen which was considered generally as an inducer of resistance.
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