| The determination of chilling requirement is a prerequisite in forcing cultivation for deciduous fruit trees, and also important foundation for selection of varieties. This study measured the chilling requirement of common pear varieties under the climatic conditions of Nanjing area. The effect of four different types of dormancy breaking reagent for dormancy breaking was examined. The effect of fruit bag and growth regulators, GA3and CPPU for fruit quality was studied. And the role of paclobutrazol (PP333) on tree growth and fruit quality was explored. The main results were summarized as following.The temperature of Nanjing fluctuates smoothly in winter, day-and-night difference swings slightly, and bears no extreme condition, which favors the accumulation of deciduous fruit trees. Chilling requirement of37pear cultivars was investigated in Nanjing by three chilling requirement calculation model. The results showed that, the<7.2℃model statistical results was higher than0～7.2℃model and Utah model, while results of0～7.2℃model and Utah model were similar, which indicated that the best chilling requirement model is Utah model. The chilling accumulation of pear varieties with chilling requirement of less than400CU would be adequate at the end of December, and it was suggested to cover film in early January for those cultivars. The chilling accumulation of pear varieties with mediate chilling requirement between400CU and700CU would be adequate in late January, and it was suggested to cover film in early February. While, those cultivars with higher chilling requirement of more than700CU was not suggested for protected forcing cultivation in Nanjing.Cyanamide (H2CN2) was the best dormancy breaking reagent among all examined ones, for breaking dormancy of ’Cuiguan’ and ’Huangguan’ branches in vitro.’Cuiguan’ detached braches flowered66. ahead under the treatment of1%cyanamide. And ’Huanguan’detached branches flowered10d ahead under the treatment of4%cyanamide. TDZ ranked the second on the effect of breaking dormancy.’Cuiguan’ detached braches flowered4d ahead under the treatment of15mg/L TDZ. And ’Huanguan’ detached braches flowered8d ahead under the treatment of30mg/L. The effect of potassium nitrate for dormancy breaking was weak.’Huanguan’ detached braches flowered only2d ahead under the treatment of8%potassium nitrate. GA3was not stable for dormancy breaking effect.’Cuiguan’ detached braches flowered4d ahead under the treatment of50mg/L GA3, but delayed under the treatment of100mg/L and150mg/L GA3. This indicated that although GA3might play a certain role in breaking dormancy, but its effect was not stable.Treatments with growth regulators, CPPU and GA3increased fruit longitudinal diameter, transverse diameter, single fruit weight, and vitamin C content. But, CPPU treatment reduced the amount of soluble solids and soluble sugar content and GA3treatment increased the soluble solids content of soluble sugar. Treatment with40mg/L CPPU increased fruit weight the most, and100mg/L GA3second. Treatment of CPPU, GA3and bagging had little effect on fruit dot density. Bagging treatment significantly reduced the size of fruit dot and the area of rust, but it was easy to form piebald fruit. Generally, growth regulator increased the size of the fruit rust which treatment of50mg/L GA3caused most serious rust. Bagging significantly reduced fruit rust area, and had little effect on other fruit qualities.The inhibitory effect of strengthening the shoot length, shoot diameter, internode length and leaf area with the improvement of the applied concentration under two kinds of application mode (foliar spray and soil application) of paclobutrazol (PP333). Foliar spray at low concentrations (200mg/L and400mg/L) improved fruit quality, and increased production. Foliar application of high concentration (600mg/L) slightly reduced fruit weight, but still improved fruit quality. Compared with foliar spray, soil application had less effect to Shoot growth. |
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