The Pear Scab Resistance And Characteristics Of Pyrus Bretschneideri Rehd. Cv. Yali (Hc)

Pyrus bretschneideri Rehd.cv.Yali originated in hebei is an ancient species with excellent and high yield characteristics. It has the high adaptability, but its disease consistance is low.The pear scab (Venturia nashicola Tanaka et Yamamoto) is one of main diseases on Yali pears, and it has been spreading almost all the Yali pear production areas in China. In recent years,pear scab has been more serious year after year and it has been become the main restrictive factor affecting the pear production. Selecting new varieties with the disease-resistance and keeping all excellent qualities have been the most economical and the most effective and the securest methods on controlling the disease. The culture history of Yali pear has several thousand years. In the long-term cultivation process,it will spontaneously produce new mutant type. Yali pear Hc is a Yali pear sprout. The results of several years investigations showed both Yali pear Hc and its grafting trees were high resistant to pear scab in field. The disease reaction type of Yali pear Hc to Venturia nashicola and its leaves structure and physiologic and biochemical index and molecular biology and the tissue culture were studied in the paper. The main results are as follows:1. In this paper, several different hormones and vitamins were used to research the growth of the Venturia nashicola in vitro. Results showed thatα-NAA,2,4-D,KT,vitaminB1 and vitamin C increased Venturia nashicola mycelium growth.The effect ofα-NAA on promoting Venturia nashicola mycelium growth was obviously.The concentration of 10mg/L ofα-NAA was the best using concentration.2. The sprouts of dormant but after hydroponic culutre and of trees in May were used as explants for the establisment of the regeneration syetem. The best explant was the sprouts from the field Yali pear Hc of mid-may. the optimum induction medium was 1/2MS+6-BA0.2mg/L+IBA0.3mg/L .3.Resistance identification of Yali pear Hc to Venturia nashicola was carried out in field when pear scab happening.The results showed that the resistance to pear scab between Yali pear Hc and Yali pear had significantly differences.Yali pear Hc showed high resistance to pear scab and Yali pear was low resistance.4. There were different leaves structure between resistant cultivar Yali pear Hc and Yali pear at different leaf stages.The leaves structure were studied included thickness of leaves,palisade tissue,spongy parenchyma,upper epidermal cell and of lower epidermal cell,cell tense ratio and spongy ratio,content of wax,density of stomata,and the comparison of leaf specific density.The result showed that the resistant cultivar Yali pear Hc leaves had high wax content,low stomata density,thick palisade tissue and the palisade tissue arranged close.Those leaf structure characters of Yali pear Hc was correlated with the resistance to Venturia nashicola. But the leaf specific density was not correlated with it.5. The content of healthful leaves chlorophyll, total soluble sugar and total soluble protein between resistant cultivar Yali pear Hc and Yali pear were compared under condition of uninfection at different leaf stages. The results indicated that the content of chlorophyll and total soluble protein in the leaves of healthful resistant cultivar Yali pear Hc were significantly higher than those in Yali pear, but the content of total soluble sugar in it was lower than that in Yali pear.6. The orthogonal design was used to optimize ISSR-PCR amplification system of Pyrus bretschneideri Rehd.cv.Yali Hc in four factors(DNA template,primer,dNTPs,and Taq DNA polymerase)at five levels respectively.The results of PCR was analyzed by software DPS 7.55,and the best level of each factor were selected.The most suitable ISSR-PCR reaction system was 1×Taq PCR Buffer[1.5mmol·L^-1 Mg²⁺],60ng DNA template,0.4μmol·L^-1 primer,0.1mmol·L^-1 dNTPs,2.0U Taq DNA polymerase in 20μL reaction system.7. Inter-simple sequene repeat-polymerase chain reaction was used to evaluate for its potential use in the identification of Yali pear Hc .10 ISSR primers selected from total 100 ISSR primers were applied with ISSR analysis to study the genetic substance differences between Yali pear Hc and Yali pear and 10 of the ISSR primers( UBC807,UBC808 , UBC810 , UBC828 , UBC829 , UBC835 , UBC841 , UBC842 ,UBC850 ,UBC851) were found to produce stable polymorphic fragments.The ISSR-PCR assay revealed total nurnber of 58 DNA bands,which of only 1 band was polymorphic (the percentage of polymorphic bands,PPB=1.72%). Yali pear Hc and Yali pear could be distinguished clearly with primer UBC810.Yali Pear Hc could produce a piece of DNA 400 bp in length,but Yali pear had no one.8.The specific fragments of Yali pear Hc was cloned and sequenced by using the primer UBC810. Six different sequences were obtained, which of three were homologous with the published ESTs of seedling leaves infected by Venturia inaequalis, seeds, flowers and fruits, the other three were new.Those functions are being identified.