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Development of Apricot Core Collection in China

Author: NingNing
Tutor: ZhangZhen；WangYuZhu
School: Nanjing Agricultural College
Course: Pomology
Keywords: Apricot(Prunus armeniaca L.) Core collection Sampling strategy SSR(Simple Sequence Repeat) Genetic diversity
CLC: S662.2
Type: Master's thesis
Year: 2009
Downloads: 45
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Abstract

China is one of primary center of apricot domestication in the world, owning very abundant germplasm resources of apricot. There are about 3000 apricot in the world and 2000 in china, comprising 9 varietas and 13 variety. The optimal sampling strategy of primary core collection of apricot from the entire cultivar collection of china was studied to estabish the primariy core collection of apricot, using 1501 accessions and 18 morphologic and agronomic traits as basic data. SSR reaction system was optimized on apricot, and genetic diversity was analysised using SSR molecular marker and morphological marker in the apricot primary core collection. Sampling scheme was established and constructed the core collection of apricot cultivars, at the same time, the validity of the core collection was detected. The results were as following:1.The appropriate entire sampling ratio was 10% for primary core collection of apricot. Under 10% entire sampling ratio, the optimal sampling scheme was grouping principle based on cultivated region combining with sampling proportion within group based on proportion of logarithm (L) when random sampling method applied within group. Using this sampling strategy to acquire the primary core collection of 150 accessions from 1501 accessions of base collection of apricot, and the primary core collection could represent the genetic diversities of the entire cultivar collection.2.The factors which affected on the SSR results apricot and comparative analysis of polymorphism of SSRs. The reaction system optimized was as follows: the 20μL reaction system contained Mg2+2.0mM/L, dNTP0.25mM/L, Primer0.20μM/L, DNA tamplate 3ng/μL, Taq DNA polymerase 0.05U/μL and PCR buffer 1 X. Polyacrylamide gel had higher ability than agarose gel in discriminating amplified fragments. To evaluate this SSR system,32 accessions of apricot were used. The 6 percent polyacrylamide gel showed that the PCR products were between 184-267bp and polymorphic in DNA among the apricot accessions, indicating that the SSR reaction system was steady and reproducible.3.The SSR primers are difficult to access and primers which come from apricot are limited.106 primers from Rosaceae plant on a preliminary screening, used five genomic DNA of apricot as a template for PCR amplification. Detected by 1% agarose,47 primers were screened from 106 primers, all of which had amplified products. Rehabilitation screen of 47 primers were used 6 varieties of apricot. After the PCR amplification, detected by 6% polyacrylamide gel,22 primers were geted finally, which had high polymorphism and stability. The number of alleles per locus varied from six to ten. Polymorphism percentage were from 50% to 88%. The results provided a powerful references for apricot resource and breeding research.4. The genetic diversity of primary core collection of apricot was studied with SSR molecular marker. Totally 22 polymorphic special primers were screened out and 196 alleles were detected, average number was 8.9. The order of genetic diversity of each cultivated region was North china warm zone>Northeast china frigid zone>Northwest china arid areas>Southwest china plateau region>Apricot of widely distributed>Tropical and subtropical. The cluster result showed that all the material were taxonomied into 6 types at 0.27 similarity coefficient and cultivated region were not differentiated and intercrossed among them.5.This study was aimed at establishing a core collection based on the analysis of SSR alleles and MOR of the primary core collection data of apricot cultivars. The index of genetic diversity, and frequency ratio of retention and loss of alleles were studied in cluster and random samples at 5 sampling ratios. The cluster sampling method preceded random sampling, and cluster sampling of SSR combined with MOR at the ratio of 80% was the best sampling strategy across sampling methods. Based on this sampling strategy,120 accessions were selected as the core collection of apricot which retained 100% alleles of primary core collection and 100% phenotypic characters. The core collection developed was evaluated by using 6 quantitative traits and the data showed that it can satisfactorily represent the genetic diversity of the original collection of 1501 apricot accessions.

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