| Pingguoli is the main cultivar planted in the frigid area in China. Because of existing demurral on its systematic status, its systematic status was studied from 2000 to 2003. Representative cultivars of Pyrus bretschneideri rehd., P. pyrifolia Burm., P. ussuriensis Maxim, P. communis L. and hybrid cultivars of theirs and pingguoli were used for testing materials .Using RAPD markers, peroxidase isozyme analysis, pollen morphology identification and statistic treatment such as cluster analysis, we systematic researched on genetic relationship and systematic status of these main pyrus cultivars and Pingguoli. Secondly, be short of pollinating trees in YanBian orchard, artificial pollination must be made. So pollen quality and pollination techniqe will directly affect its fruit—setting rate. How to pledge pollen quality and quantity and studying on pollination and fecundation process correlated with its fruit—setting have become these problems which should be solved immediately. Therefore, mass collection, transportion, storage technique and features of pollination and fertilization were also studied . Main research results as followed: 1. Establishing the most suitable RAPD reaction system of pear : including Tris—HCl(pH9.0)10mmol/L, 50mol/LKCl, 2.0 mmol/L MgCl2, dNTP 200μmol/L, template DNA 10 ng, primer 10pmol, Taq DNA ploymerase 1.5U in the 2.5μl reaction system. The appropriate augmentation procedure is: predenature 2 minutes at 94℃,denature 1 minute at 94℃,anneal 1 minute at 37℃, extent 2 minutes at 72℃,five cycles; denature 0.5 minute at 94℃,anneal 1 minute at 37℃, extent 2 minutes at 72℃,forty—five cycles; extent 10 minutes at 72℃. 2. RAPD analyses were done on 40 pyrus cultivars and types. Twelwe primers were culled from 100 random 10bp primers and were used to expand. We expanded 146 DNA bands, in which, there were 141 polymorphic DNA bands, accounted for 96.6%, one primer may expand 12.2 bands on average. There was one or over cultivar—specific markers in 24 pyrus cultivars, which were used to identify cultivar or preselect early charcters.3. According to the results of amplified DNA, cultivars and types of 40 pyrus were analyzed by using cluster analysis and were classified into 7 types. Meanwhile , results showed that pyrus communis L. originated in Europe could be distinctly distinguished from P. bretschneideri Rehd., P. pyrifolia Burm. and P. ussuriensis Maxim, which originated in China. Though three Chinese species were not clustered into different groups respectively, there were different genetic distances between any two materials. Hence, the technique of RAPD may use scientific basis for classification and identification of pyrus species. 4 . Pingguoli was clustered together with Yali, Qixia Daxiangshui, which representative cultivars of P. bretschneideri Rehd. system, but, it showed relative far gentic distances between representative cultivars of P. pyrifolia Burm. and P. ussuriensis Maxim, meanwhile, it showed the same result with hybrid cultivars(No.2 Zaoxiang)of them. Therefore we concluded that pingguoli should belong to P. bretschneideri Rehd. system at the molecular level . 5. Using the technique of peroxidase isozymic, we researched on 56 pyrus cultivars and types and analyzed their cluster patterns and similar coefficient, the results showed: pyrus communis L. originated in Europe could be distinctly distinguished from P. bretschneideri Rehd., P. pyrifolia Burm. and P. ussuriensis Maxim, which originated in China. Though three Chinese species were not clustered into different groups respectively, there were different genetic distances between any two materials. The 56 cultivars were classified into 8 types, the majority agrees with the traditional results. Hence, the technique of POD may use scientific basis for classification and genetic relationship of pyrus species. 6. We compared peroxidase isozymic cluster patterns and similar coefficient, the results showed that Pingguoli and its variety ─Dongning No.5 Dali clustered together with Qixia Daxiangshui, then together with major cultivars of P. bretschneideri Rehd. system. So we considered that there was high similarity between Pingguoli and P. bretschneideri Rehd. system at the level of genetic relationship. 7. There were same characters in the pollen morphology of pyrus. The significant differences existed in the shape,size and strip ornamentation of pollen grains. Pollen polar axis of P. communis L. is very short, strip ornamentations show followed characteristics: the hole is big and thick, many lines are convolute, perforations are excessive and theirs shapes are various. The strip ornamentations on the surface of Pyrus bretschneideri rehd., P. pyrifolia Burm., P. ussuriensis Maxim,are very similar, that is to say, lines are smooth, ridges are very narrow, perforations are very few. Based on the clustering analysis of pollen morphological and quantitative characteristics, some cultivars didn't agree with the traditional results. Hence, we believed that palynology only provided the reference for the identification of varieties. 8. Though the size and shape of pingguoli are special, its strip ornamentation is more similar with Yali which belongs to P. bretschneideri rehd. system. So it is reasonable that pingguoli belongs to P. bretschneideri rehd.system. Moreover, Chaoxianyangli has genetic relationship with P. communis L. system and P. pyrifolia Burm. System; Shenbuzhi is more inclined to P. communis L. system; Nanguoli should belong to P. ussuriensis Maxim system. 9. The best collection time of pollinating pollen for Pingguoli is the big bud period; the germination rate of the pollen collected by mechanism threshing is the highest while the losing rate is the lowest, pollen dried in the room has the highest germination rate,the higher the temperature is, the lower germination rate is; the thinner the thickness of anther is, the higher germination rate is. The germination rate of pollen transported in refrigeration car is higher 15.2% than that of the regular transported pollen. The germination rate of pollen which has been stored in freezing room of refrigerator for one year has no distinct difference with pre–storage, it exceeds 65.5%, meanwhile, its fruit—setting rate has no natable difference with the fresh and same germination rate pollen,its fruit—setting rate of inflorescence exceeds 86.6%. The germination rate of pollen which has been stored in cold storage room of refrigerator in a dry and sealed condition exceeds 39.8%, and its fruit—setting rate of inflorescence exceeds 50.5%.
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