The rubber tree (Hevea brasiliensis) is the world’s major source of natural rubber. An expedition to the Amazonas and Para states by the Rubber Research Institute of Malaysia (RRIM) in 1995 led to the successful collection of more than 50,000 genotypes from different locations of the states to broaden the existing gene pool. Realising the severe limitations faced with large germplasm, a core collection consisting of a reduced number of genotypes derived from a base collection of 505 selected genotypes was developed. The genotypes were first sorted based on their relative contributions to the total variability by principal component scores of a set of 11 quantitative traits. Then, the cumulative proportion of their contributions to the total variance was computed. The size of the core set was decided by a cut-off value when the rate of increase in cumulative contributions reached a maximum value and began to decline. Entries with a high degree of similarity in the selected core collection were eliminated using Gower metric coefficient. Shannon–Weaver diversity index of 14 morphological qualitative descriptors was used to verify the size and choice of entries in the final collection. As a result, 25.35% of the base collection or a total of 128 genotypes (73 from Manaus, 17 Manicore, 13 Atalaia do Norte, 11 Borba, 8 Benjamin Constant, 3 Tapajoz, 2 Belem, and 1 Iranduba) were selected to be included in the final core collection. Establishment of the core collection of this germplasm will enable a more rapid and effective utilisation of these genetic materials in the rubber breeding programme.

中文翻译：

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1995 RRIM橡胶树种质的橡胶树核心提取物，可有效地用于橡胶育种计划

橡胶树（巴西橡胶树）是世界上天然橡胶的主要来源。1995年，马来西亚橡胶研究所（RRIM）对亚马孙州和帕拉州进行了一次考察，成功地从该州的不同地点收集了50,000多个基因型，以扩大现有的基因库。由于认识到大型种质所面临的严峻局限，开发了一个核心集合，该核心集合由数量减少的基因型组成，这些基因型来自505个选定基因型的基本集合。首先根据11种定量性状的主成分评分，根据基因型对总变异性的相对贡献对基因型进行分类。然后，计算出其贡献在总方差中的累计比例。核心集的大小由累积贡献增加率达到最大值并开始下降时的临界值决定。使用Gower度量系数，可以消除所选核心集中具有高度相似性的条目。使用14种形态定性描述符的Shannon-Weaver多样性指数来验证最终集合中条目的大小和选择。结果，选择了25.35％的碱基库或总共128个基因型（来自Manaus的73个基因，17个Manicore，13个Atalaia do Norte，11个Borba，8个Benjamin Constant，3个Tapajoz，2个Belem和1个伊朗杜巴）被选为基因型。包含在最终的核心收藏中。建立这种种质的核心种质将使橡胶育种计划中的这些遗传物质得到更迅速和有效的利用。