The Study On Isolation, Identification And Regularity Of Development Of The Pathogens Of Blackhead Disease Of Kuerle Pear During Storage

There is a new disease which appears in the Kuerle fragrant pear during storage. It is named "Blackhead Disease" by local farmers.The survey showed that its incidence rate is 4% to 10%, and it's occuring from February to April of the second year during storage. Now the reason of "Blackhead disease" isn't clear, and there is lack of effective preventive measures. So, this studying is based on the material of Pear. And separating and depurating the "Blackhead disease", then inoculated with pathogenic bacteria into the pears. The major pathogen was identified by morphological characters and internal transcribed spacer (ITS) analysis, and the studying of biological characteristics; In order to founding the occurrence regularity, the pathogenic bacteria is inoculated back into good pear, then storage in post-harvest under different environments(refrigeration, controlled atmosphere storage and room temperature storage). Finally, in order to get the reasons about the "Blackhead disease" of Pear, I make the preliminary study,which is about the determination of quality, physiological,mineral elements and activity on the main resistance etiology in the different parts of pear. The preliminary studies can provide a theoretical basis for disease-resistant and prevention. The main results are as follows:1 Isolatiing and Identifing of the Pathogen:Seven species were found. They were classified in the Cladosporium, Penicillium, Alternaria, Aspergillus genuses. And the morphological characters and internal transcribed spacer analysis showed that Fungi Deuteromycotina Hyphomycetes Hyphomycetales Dematiaceae Cladosporium herbarum Link were the major pathogen of root rot of the"Blackhead disease".2 Experimental studying on pathogenicity of pathogens showed that:Researches showed that the calyx of the pear causes the disease easily; While its carcass and its tail are difficult to cause the disease; And the male pears is easier to cause the disease than the female pears; And vaccination injury prone pears is easer to cause the disease than the incidence of non-inoculated wounds ones.3 Blackhead disease of Pear biological properties of bacteria:The results indicated that the beneficial for both growth of mycelium and product of conidia in pear juice (20%) medium; the suitable temperature for mycelia growth and spores germination is 5℃-40℃; the optimum temperature for mycelia growth and spore production is 25℃; the optimum pH was 7.0; Under the continuous lighting, the growth of pathogenic bacteria colony diameter is faster; experiments about nitrogen and carbon shows that nitrogen (ammonium nitrate and sulfuric acid ammonium) and carbon source (lactose and mannose) of the pathogen is inhibited. The optimal nitrogen source is ammonium chloride, peptone, urea and yeast extract, the optimum carbon source for the soluble starch, glucose and glycerol; The pathogen will be died at 65℃in the deadly temperature test; the death rate gradually increased with UV radiation time, and the mortality rate was 98.8% by irradiation for 9 minutes.4 Occurrence regularity about blackhead disease of Pear inoculated pathogenic bacteria under different storage conditions:The disease incidence period of pear, the lesion area and the speed of area expansion are different at three different Storage Environment. That is, under room temperature storage conditions, the disease incidence period of pear is shorter, High incidence;the lesion area and the speed of area expansion is faster; then followed by cold storage, and finally to atmosphere storage; The incidence of female pear is higher than male pear at three different storage conditions.5 The studying of the reasons about "Blackhead Disease" in preliminary:compared with blackhead disease pear and good pear, the studies showed that the quality of male pear is higher than that of female pear; So the male pear has more stronger resistance, and more difficult to be infected by pathogens than that of the female pear; the content of N, P, K, B, N/Ca and K/Ca are higher,but Ca is lower. And it is negatively correlated which the content of Ca and N and K; Three enzymes' activity about PPO, POD and PAL are increased which inoculated with Cladosporium herbarum Link at pear, its activity is positively correlated with the formation of lesions increasing, PPO and POD activity at the lesion and outside the 5mm are above the 5-10mm; PAL activity of outside the 5mm and outside 5-10mm are above the lesion.