Morpho-Diversity Assessment of Coffea canephora Accessions in Nigeria: Trait-Based Characterization for Genetic Improvement

Background Coffea species (Coffee) is one of the most economically important agricultural commodities universally. In Nigeria, Coffea canephora is the dominant species, accounting for about 95% of coffee exports, yet its morphological diversity remains poorly documented. Understanding phenotypic variability is vital to developing novel breeding programmes for crop improvement. This study therefore assessed the morpho-diversity of C. canephora accessions collected from three agroecological zones in Nigeria. Results Forty-three accessions of C. canephora comprising six canephora classes: Gold Coast, Java Robusta, Java ex-Gamba, Kouillou, Niaouli, and Uganda Robusta were characterised, using thirteen morphological traits (four quantitative and nine qualitative) following International Plant Genetic Resources Institute descriptors. Plant height ranged from 10.84 cm to 47.89 cm, while leaf width varied from 5.93 cm to 13.20 cm. Leaf length and leaf width were strongly correlated (r = 0.617, p < 0.001). The first four principal components explained 100% of total variance, with plant height contributing 65% and leaf length 21%. Cluster analysis grouped the accessions into three distinct classes, with 40 accessions expressing broad genetic variation, one genetically distinct accession, and two closely related accessions separating from the main population. Qualitative traits revealed meaningful variation in plant habit, branching pattern, leaf shape, and berry characteristics. Conclusions Substantial morphological diversity exists among C. canephora accessions in Nigeria, with plant height and leaf length identified as the principal phenotypic traits for discriminating accessions. These findings provide a foundational trait-based framework for selecting superior accessions and designing targeted genetic improvement programmes for Nigerian robusta coffee.