Comparison of optimum sampling intensities of core collections in selected cross- and self-pollinated and asexually propagated crops
2008
Salazar, K.S.
The concept of developing a core collection involves identifying a subset of manageable size from a germplasm collection, which is as representative as possible of the total genetic-diversity in the base collection. This study investigate the optimum sample size of three crops under different breeding systems namely, corn, a cross-pollinated crop; rice, a self-pollinated crop and sugarcane, an asexually propagated crop. The Ward's minimum variance method was used in farming the clusters of accessions of each crop and the D allocation method was utilized in determining the number of accessions to be selected from each cluster. Results showed that sugarcane, which exhibits the highest number of homogeneous groups of accessions of 5 clusters. Only 3 and 4 clusters were formed for corn and rice base collection, respectively. One thousand core collections at different sampling intensities were obtained from each crop. The genetic diversity between accessions of the core collection was measured using the mean Gower distance. A sampling intensity was considered optimum if the core collection produced, on the average, a mean difference at most 20% and a coincidence rate of range at least 80%. It was found that the amount of difference in the mean between the core and the base decreases and the amount of range captured by the core from the base increases, as the size of the core increases. Results showed that core collection of corn should contain the 48% of the accessions in the base collection. On the other hand, the optimum sampling intensity intensified for rice and sugarcane are 20 and 35%, respectively.
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