Identification Of Resistance To The Pear Scab On The Different Cultivars And Its Regularity Of Occurrence

Pear scab is one of the main diseases on pear, but also the widespread occurrence of disease on the world. It often occurs in different areas for pear production in China. Over the years, Xinyi City, pear production has been affected by pear scab and the majority of growers suffered greater losses for this. In order to reduce damage caused by pear scab, find out regularity of pear scab occurrence, and do a good job of prevention and disease-resistant varieties of identification screening, this study investigated the different species, different times, different management, different planting densities, different tree potentials and ages, and different preventions for pear scab, and studied the special germplasm resource Xinfeng pear, which is autoimmune to pear scab, and its systemic cultivation techniques. The conclusion is as following.1. The characters of thirteen cultivars resistance to pear scab were identified by natural and artificial inoculation and the results showed that different cultivars had the different resistance to pear scab. Identification by natural inoculation showed that leaves and fruits of Xinfengli and Bartelett were both autoimmune; fruits of Housui, Kisui, Zaosu and Okusankichi were immune to pear scab; leaves of Housui, Kisui, Zaosu and Okusankichi showed high resistance to pear scab; leaf of Chili showed middle resistance; leaves and fruits of Huangxiang, Huangguan and Xianli all showed middle resistance; whereas leaves and fruits of Dangshansuli, Changbali and Yali were all susceptible. Identification by artificial inoculation showed that leaves and fruits of Xinfengli and Bartelett were both autoimmune as well; fruits of Housui, Kisui, Zaosu, Okusankichi and Chili were immune to pear scab; leaves of Housui, Kousui, Zaosu pear and Okusankichi showed middle resistance; whereas leaf of Chili was susceptible; leaves and fruits of Huangxiang, Huangguan and Xianli were all susceptible; leaves and fruits of Dangshansuli, Changbali and Yali were highly susceptible to pear scab. The results of two identifications were coincident except a little difference.2. Systemic observation on the botanical and biological characters of Xinfengli, a special germplasm resource in local that is resistant to pear scab, has been done, and demonstration and extension of Xinfengli has also been executed. The cultivar showed big fruit, large and thick leaves, strong tress, high resistance to diseases and insect pests, and extensive adaptability; and was planted extensively in Dafeng city of Jiangsu Province, Shandong province, Henan Province, Hebei Province, Anhui Province, Shanxi Province, and so on. The key cultivation techniques for Xinfengli pear were systemically summarized in the five aspects:orchard establishment, fertilizer and water management, shaping and pruning, management of flowers and fruits, disease and pest control. In addition, Xinfengli pear was triploid, identified by flow cytometry.3. Setting up a disease prevention and treatment of normal field for control, the prevalence situation for pear scab was systemically observed between the year 2006 and 2007, with Dangshansuli as investigation object, which was susceptible to pear scab in the main orchards. Dynamic graph of pear scab occurrence was constructed. The results indicated that pear scab occurrence in Xinyi city was mainly in first and middle ten days of May and middle ten days in August or so. The strength and the period of pear scab was closely related to the temperature, humidity and rainfall according to the meteorological information during that period. High temperature in summer was helpful to the disease control. Pear scab was controlled to a certain degree, though regularity of occurrence in orchard with normal disease prevention was similar to the orchard as a control in the experiment.4. Pathogenic factors of pear scab were investigated on the Yali, Dangshansuli and Changbali in the following aspects:different tree potentials, the extent of cleaning the orchard, inner or peripheral locations, different planting density. The results showed that the diseased fruit rate and diseased leaf rate were 13.7% and 18.6% respectively, and fruit and leaves of the disease index were 5.3 and 6.17 on Yali trees with weak tree potential whereas the diseased fruit rate and diseased leaf rate were 7.9% and 7.8%, and fruit and leaves of the disease index were 2.60 and 3.04 on Yali trees with middle tree potential; the diseased fruit rate and the disease index in Dangshanli cleaning orchard in spring and fall were 16.75%,13.5%,4.26 and 3.94 respectively whereas the diseased fruit rate and the disease index in the corresponding orchard with cleaning the orchard drastically were 4.75 and 1.01; the diseased fruit rate and the disease index in Dangshansuli cleaning orchard in spring and fall were 14.75%,15.25%,4.07 and 4.26 whereas the diseased fruit rate and the disease index in the corresponding orchard with cleaning the orchard drastically were 5.25% and 1.73; the disease rate of peripheral leaves of Dangshanli trees was 7.9% lower than that of inner leaves and the disease rate of peripheral leaves of Yali trees was 6.9% lower than that of inner leaves; the diseased fruit rate of Changbali fields with different planting densities 5 m x 4m,5m x 3m,4m x 3m,4m x 2m long the fruit of the pear rates were 12.7% and 16.4%,18.7%,26.6% respectively and disease index were 1.96,2.84,4.13, 5.01; the diseased fruit rate werel3.4%,16.5,20.6% and 22.8%,and disease index were 2.03,2.26,3.45 and 4.27 for Yali fields with the same planting density. It indicated that stronger tree potential was corresponding to stronger resistance to pear scab; the disease was weaker in the orchard cleaning drastically; the extent of disease in peripheral location was lighter than that in inner and the high density was related to heavier disease. Results of this study would be helpful to control pear scab and to utilize the special germplasm resource resistant to pear scab.