Construction of core collection of Alnus nepalensis in Yunnan based on SRAP molecular markers
[Objective]The suitable construction strategies of core collection of Alnus nepalensis were screened by comparing the effectiveness and representativeness of the proton collection of A.nepalensis species constructed at different sampling ratios.[Method]Using half-sib off-spring of superior trees of A.nepalensis as test materials,6 sampling ratios were set(10％、15％、25％、35％、45％and 55％),and Nei's genetic distance and the improved minimum distance stepwise sampling method were used to construct the proton collection,and 4 genetic di-versity indexes were used to analyze the representativeness of proton collection to the original germplasm.The mean t-test and variance F-test were used to analyze the homogeneity of the variation between the seed proton set and the original collection,the correlation coefficient was used to analyze the correlation between the seed proton set and the original collection,and the core collection was confirmed by genetic dis-tance comparison and cluster analysis.[Result]The number of polymorphic loci,percentage of polymorphic loci,number of observed alleles,and allele retention rate of the germplasm subset constructed with a 25％sampling ratio were consistent with the original germplasm set.The other four evaluation indices were significantly higher than those of the original germplasm set,moreover,the correlation coefficients between mean and variance of the germplasm subset and the original germplasm were close to be equal to 1,with an average genetic distance increase of 16.82％compared to the original germplasm set.Therefore,it was believed that the germplasm subset constructed at a 25％sampling ra-tio could effectively represent the original germplasm.[Conclusion]Considering the validity,practicability,cost and workload of the core col-lection,it was considered that the core collection of A.nepalensis constructed based on 25％sampling ratio could fully represent the genetic diversity of the original collection.
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