Genetic diversity of promising ‘conilon’ coffee clones based on morpho-agronomic variables

Abstract Knowledge of the genetic variability of a population is essential to guide its preservation and maintenance in addition to increasing the efficiency of genetic breeding programs. On this basis, this study was conducted to evaluate the genetic diversity of Coffea canephora genotypes using multivariate statistical procedures applied to a set of morpho-agronomic variables. The materials employed in this study constitute a crop located in Vila Valério - ES, Brazil, where the genotypes are arranged in a randomized-blocks experimental design with four replicates. Significant differences were detected by the F test at the 1% or 5% probability levels among the genotypes for all evaluated traits, demonstrating heterogeneity of genetic constitution in the studied population, which is favorable to breeding, as it indicates the possibility to identify superior and divergent individuals. Based on the generalized Mahalanobis distance, the most divergent combinations were obtained between genotypes 23 and 10 (256.43) and 23 and 17 (250.09). The clusters formed by Tocher’s optimization and the UPGMA hierarchical method agreed, both similarly grouping the genotypes into three clusters. Of the analyzed traits, mature fruit weight (19.08%), yield (15.50%), plant diameter (12.42%), and orthotropic-shoot internode length (10.94%) were the most efficient to explain the dissimilarity among the genotypes.摘要 了解种群的遗传变异，不仅能够提升遗传育种项目的实施效率，同时也是指导种群保护与存续的必要基础。基于此，本研究借助一组形态农艺性状的多元统计分析方法，对罗布斯塔咖啡（Coffea canephora）的基因型遗传多样性展开评估。本研究所用试验材料种植于巴西圣埃斯皮里图州维拉瓦莱里奥（Vila Valério - ES, Brazil），供试基因型采用随机区组试验设计，设置4次重复。经F检验，所有供试性状在不同基因型间均表现出1%或5%显著性水平的差异，表明供试种群的遗传构成存在异质性，这对遗传育种工作十分有利，说明可从中筛选出优良且遗传差异显著的个体。基于广义马氏距离（generalized Mahalanobis distance）的计算结果，基因型23与10（256.43）、23与17（250.09）的遗传差异最为显著。采用Tocher优化法（Tocher’s optimization）与UPGMA层次聚类法得到的聚类结果一致，均将供试基因型划分为3个类群。在所有分析性状中，成熟果实重量（19.08%）、产量（15.50%）、植株冠径（12.42%）以及直立枝节间长度（10.94%）是区分不同基因型遗传差异的最有效性状。