Study On The Genetic Diversity Of Winterhardy Apple And Pear Germplasm Resources

In the present dissertation, 292 winterhardy apple accessions and 210winterhardy pear accessions conserved in the national fruit germplasm Gongzhulinghardy fruit nursery were employed as the experimental materials to describe theirphenotypic characters including tree posture, tree type and characteristics ofone-year-old branch, leaf, flower and fruit; to evaluate and determine their biologiccharacteristics including phenological period (phenophase), sprouting rate, branchingability, cropping efficiency, dwarfing ability, fruit quality, cold-resistance,disease-resistance and chromosome ploidy; so that the phenotypic genetic diversitywas found.On the base of phenotypic results, the database about winterhardy apple and peargermplasm resources was set up and submitted to E-deck constructed by the nationalscience and technology ministry in order to provide the broad share and utilization.RAPD technique was used to make molecular marker in all experimentalmaterials so that the phenotypic genetic diversity was screened and verified, then thegenetic diversity of winterhardy apple and pear was further revealed in molecularlevel. Combining the result in molecular marker and the experience accumulatedduring the past 50 years in winterhardy apple and pear breeding, the core collectionsin winterhardy apple and pear were first constructed and the particular RAPDmolecular markers were gained from winterhardy apple and pear germplasmresources.By the further analysis of the research results, we proposed that the hybridprogeny (group) in winterhardy apple resources maintained at the repository wasclassified by itself and formed a new serial -- hybrid group serial in Sect. Malus; onthe cluster graph, M. komarovii had long distance with M. kansuensis illustrated thefar genetic relationship, and short distance with M. baccata illustrated the closegenetic relationship. In fact, both M. komarovii and M. baccata originated atChangbai mountain area, but M. kansuensis originated at Gansu province, so thegeographic distance between two origin places is very big. Because Pingguoli andKuerlexiangli were clustered together with Pyrus bretschneideri, so these varietiesillustrated the near relationship with P. bretschneideri, then were assorted into thesystem of P. bretschneideri.By the all research results above, the scientific foundation was made for furthergermplasm resource research, speedup of breeding procedure, parent selection, early stage identification and so on. Main results were as follows:1. The basic information of 502 winterhardy apple and pear accessions wascollected by the detailed investigation of botanic characters including tree posture,tree type and characteristics of 1-year-old branch, leaf, flower and fruit; and theevaluation and determination of their biologic characteristics including phenologicalperiod (phenophase), sprouting rate, branching ability, cropping efficiency, dwarfingability, fruit quality, cold-resistance (hardiness), disease-resistance and chromosomeploidy. Then, substantial genetic diversity was found in many (phenotypic) characters;i. e. from tall arbor to bush, from big to small fruit, from yellowish to strong redpericarp, from upright to drooping tree posture, from sour, astringent, bitter to sweetfruit flavor, from low to high productivity, from strong to weak cold-resistance, fromstrong to weak disease-resistance and so on. All of these results made it possible to setup the database and to construct the preliminary core collections among winterhardyapple and pear germplasm resources.2. By the analysis and measuration of soluble solid content, sugar content, acidcontent and vitamin C content in the fruit of winterhardy apple and pear germplasmresources, the genetic diversity was verified in the characters above. General speaking,the content of soluble solid, sugar, acid and Vitamin C of the small and middle-sizefruit in apple resources were higher than those of big-size fruit, that is, the order fromhigh to low content in fruit was M. baccata > M. asatica > hybrid progeny > M.domestica.3. By the evaluation and determination of cold-resistance about winterhardy appleand pear germplasm resources, the apple resources of strong cold resistance were M.baccata Borkh., M. mandshurica (Maxim.) Kom., M. komarovii (sarg) Rehd.,Xiaosuanguo and M. prunifolia Borkh. which had the genetic relationship with M.baccata Borkh. or M. mandshurica (Maxim.) Kom., but apple resources with big-sizefruit e. g. Lvxiangjiao, Danpingyihao, which had the genetic relationship with M.domestica or M. sieversii, had the weak cold resistance; the hybrid progeny betweenM. prunifolia Borkh. and M. domestica e. g. Jinhong, Longguan, had the moderatecold resistance and displayed the normal distribution. In the winterhardy pearresources, P. ussuriensis Maxim. had the strong cold resistance, then P. bretschneideriRehd. middle; and then P. communis L. had the weak cold resistance. The hybridbetween P. ussuriensis Maxim. and P. bretschneideri Rehd. or P. communis L. had themoderate cold resistance and displayed the central tendency variation, but some individuals displayed super-parent heredity. The resources with the strongest coldresistance could resist minus 45℃.4. By the evaluation and determination of disease-resistance about winterhardyapple and pear resources, the resources with the strong resistance to apple canker wereM. komarovii, Zha'aishandingzi, Xiaohuanghaitang, Huangtaiping, Xiaosuanguo andDaqiu; the resources with the strong resistance to pear scab were Suanliguozi,Zhenhongxiao and Xifengjingbai, which were very good winterhardy pear germplasmresources. It was also found that the resources which had good cold resistance alsohad the good disease resistance; there was the positive correlation between thecharacters. These results could make a good scientific base for further research,construction of core collections and utilization in breeding about winterhardy appleand pear germplasm resources.5. By the determination of chromosome ploidy on winterhardy apple and peargermplasm resources, all of the experimental materials belonged to diploid 2n=2x=34, no matter species, fruit or leaf.6. Based on the results of phenotypic character description, evaluation anddetermination, the database was set up about winterhardy apple and pear germplasmresources.7. Using the winterhardy apple and pear germplasm resources, RAPD reactionsystem and optimizing reaction procedure were established, 25 primer were selectedand used in 266 apple accessions and 107 pear accessions. The percentage of thepolymorphism bands by RAPD amplifying was 93.47% and 96.20% for apple andpear respectively. By the Nei-Li genetic distance, 180 apple accessions and 87 pearaccessions were analysis and calculated the value of the genetic distance, which was0.0891 to 1.000 in apple (average value 0.00506) and 0.040 to 0.4269 in pear (averagevalue 0.1394). In apple resources, Jinhong4hao and Jinhong7hao had the smallestgenetic distance 0.08911, but M. kansuensis and LingDangGuo had the biggestgenetic distance 1.0000. In pear resources, Suanliguozi and Longliangli had theminimum genetic distance 0.040, however, Heilongjianghonghuagai andYuandongyihao had the maximum genetic distance 0.4269.8. By the analysis of cluster graph, it was found that Sect. M. baccata, Sect. M.prunifolia and Sect. M. kansuensis had the close genetic relationship which was samewith the classic taxology. But the phenotypic genetic diversity was very rich(abundant) in the Malus resources. Because the phenotypic character between M. baccata and M. prunifolia was close, they had the nearest genetic relationship. It wasverified that M. prunifolia was the hybrid between M. baccata and M. domestica,which was reported before. But there were obvious differences between M.kansuensis or M. komarovii and M. baccata in the phenotypic characters. Combinedwith the analysis of the cluster graph, the present author proposed that M. kansuensisand M. komarovii were derived from the cross of Malus and Crataegus because Malus,Pyrus, Crataegus and Sorbus had the same ancient species. About pear, there wasalso the abundant phenotypic diversity. Because Pingguoli and Kuerlexiangli wereclustered together with P. bretschneideri, and illustrated the near genetic relationshipwith P. bretschneideri, so they were assorted into the system of P. bretschneideri.9. According to the classic taxology, hybrid progeny in winterhardy appleresources was formed a new series -- hybrid group series in Sect. Malus.10. According to the results in botanic and biologic investigation, evaluation anddetermination, and the result in RAPD molecular marker, core collections inwinterhardy apple and pear germplasm resources was constructed, which were 46accessions in apple and 29 accessions in pear.11. Particular RAPD markers were gained from winterhardy apple and peargermplasm resources.