| Pear ring rot is one of the major diseases which happened not only on pear fruits but also on apple trees, peach, almond, crab apple, hawthorn, Chinese date and so on. It is an important problem facing to a lot of fruit producing areas in many countries and regions. In this paper, we studied biological characteristics of Botryosphaeria berengeriana f.sp. piricola, the relationship between different pear varieties and Botryosphaeria berengeriana f.sp. piricola, the inhibition of2biocontrol bacteria against Botryosphaeria berengeriana f.sp. piricola and molecular identification of their species, effect on the system of antioxidant enzymes of Botryosphaeria berengeriana f.sp. piricola and biocontrol bacteria on pears. The results made us know clearly about pear ring rot and its influence on pear fruits. We also conducted researche on the prevention and treatment of Botryosphaeria berengeriana f.sp. piricola with biocontrol bacteria, and at last, we screened the best biocontrol bacteria which could provide certain academic and practical basis to resolve actual problems in yield. The research contents were as follows:(1) We chose pear ring rot branches from Nanjing Jiangsu pear orchards.Academy of Agricultural Sciences. After tissue isolation and spore purification, we backed the strains inoculated on pears which based on Koch’s rules and at last gained twenty strains P-1～P-20(P-1～P-10:Nanjing Jiangpu; P-11～P-20:Jiangsu Academy of Agricultural Sciences).The biological characteristics of Botryosphaeria berengeriana f.sp. piricola were studied. The results showed that different strains have different growth rate, pathogenicity and sporulation quantity. P-16had the maximum daily growth rate and P-10had the minimum, P-16had the most powerful pathogenicitiy and P-10had the weakest, P-7、 P-13、P-16had the largest sporulation quantity, but P-4、 P-10、P-19produced no Pycnidium.The optimum temperatures for mycelium growth, sporulation and conidial germination were28℃,25℃and28℃, respectively. Daylight lamp and Dark light lamp were beneficial to mycelium growth, dark condition go against mycelium growth, whereas black light lamp condition could promote sporulation. However, the conidial germination showed to be less affected by light conditions. The proper pH values for mycelium growth, sporulation and conidial germination were7～9,6～8and7～9, respectively. The lethal temperatures for mycelium and conidiospore were62℃(10min) or57℃(15min), and60℃(10min) or55℃(15min).(2) The relationship between14pear varieties and20different pear ring rot strains were studied. The results showed that:different pear varieties had different resistance reflection:Jinshuiqiu, Wansanji and Dangshan were disease-resistant variety (R), Cuilv, Huanghua, and Pogua were belonged to moderate resistance (MR), Zhongcui, Jushui, Jinhua and Xingao were moderate susceptibility varieties (MS), Qiyuesu and Zaomeisu were susceptible cultivars (S), and at last, Xishui and Jin twenty century were highly sensitive cultivars(HS). There has a certain association between pear varieties’maturity and resistance. Most Rs and MRs were late varieties;meanwhile, most MS,SH,and S were early or middle varieties; furthermore, there was certain specialization existing between different pear ring rot strains and pear varieties, and different strains had significant pathogenicity differentiation among pear varieties, in which P-15had the most serious pathogenicity differentiation and P-18had the least. Moreover, the20isolates of Physalospora piricola Nose could be divided into three categories:strong(pathotype I), intermediate(pathotype Ⅱ)and weak pathogenicity(pathotypeⅢ)respectively, in which P-11had the most powerful average pathogenicitiy and the average pathogenic disease spots was35.4mm, on the contrary, P-4had the weakest pathogenicity and the average pathogenic disease spots was23.9mm.(3)2biocontrol bacteria Sf-19,Sf-28were screened from our laboratory, and the inhibition effect of their different concentration treatment on mycelium growth, spore germination and pathogen inoculated on pears against Botryosphaeria berengeriana f.sp. piricola were studied. The results showed that stock solution of Sf-19was the best, the inhibition rate on mycelium growth, spore germination were87.33%and97%respectively. The inhibition rate of pathogen inoculated on pears, protection test(Ⅰ):71.97%, therapeutic experiment (Ⅱ):64.92%; stock solution of Sf-28was the second best, the inhibition rate of mycelium growth, sporulation quantity were87%and80%respectively. The inhibition rate of pathogen inoculated on pears, protection test(Ⅰ):64.54%, therapeutic experiment (Ⅱ):59.21%. With the growing times of dilution, the inhibition effect of biocontrol bacteria decreased. The inhibition rate of mycelium growth, spore germination of106times diluent of stock solution of Sf-19were68.67%and3%respectively, The inhibition rate of pathogen inoculated on pears, protection test(Ⅰ):10.01%, therapeutic experiment (Ⅱ):9.12%; The inhibition rate of mycelium growth, sporulation quantity of106diluent of stock solution of Sf-28were60%and5%respectively, The inhibition rate of pathogen inoculated on pears, protection test(Ⅰ):9.23%, therapeutic experiment (II):9.09%. Through comprehensive comparison between the2biocontrol bacteria, Sf-19was better than Sf-28.At last, the molecular identification showed that the2biocontrol bacteria were both Bacillus Subtilis.(4)We inoculated Botryosphaeria berengeriana f.sp. piricola and spray biocontrol bacteria on pears, aiming to determine the change of the system of antioxidant enzymes. The results showed that:inoculated Botryosphaeria berengeriana f.sp. piricola and spray biocontrol bacteria on pears had certain effects on the system of defense enzymes. Treatment L and L+S were more effective than treatment S and W on MDA; treatment S、 L、L+S were more effective than treatment W on SOD、CAT and POD, but compared with SOD and POD, CAT had less range of effects; treatment S had little effect on PPO, but treatment L、L+S were more effective than treatment W. |
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