Phenotypic characterization of some Nigerian Coffea species using morphological characters

Accurate assessment of phenotypic diversity is essential for the effective conservation and genetic improvement of Coffea spp. and so far little work has been done on it in Nigeria. We studied the morphological characterization of 48 coffee accessions comprising one each of C. arabica, C. abeokutae, C. liberica and C. stenophyla; 14 accessions of C. canephora from the Cocoa Research Institute of Nigeria; and 30 landraces collected from Ekiti and Kogi states in Nigeria. The agro-morphological traits used were classified into quantitative (plant height, stem diameter, leaf length, and leaf width) and qualitative (plant habit, branching habit, leaf shape, leaf apex shape, young leaf colour, mature leaf colour, berry shape and berry colour) traits. Significant variation was observed across all quantitative traits (p < 0.001), with notable divergence in plant height, stem diameter, leaf length, and leaf width. Principal Component Analysis (PCA) revealed that the first three components explained 94.4% of total variation, with leaf and stem traits contributing mostly to the variance. Cluster analysis of the quantitative traits grouped the accessions into three distinct clusters and one outlier, indicating the presence of phenotypic diversity among the accessions, while their correlation analysis highlighted strong associations between key growth traits, notably between leaf length and width (r = 0.69, p < 0.01). Multiple Correspondence Analysis (MCA) of qualitative traits revealed clear associations between accessions and trait categories. Landraces clustered around bushy growth habit, elliptic leaves, and red berries, whereas distinct species such as Coffea stenophylla and Coffea liberica were separated by tree habit, lanceolate leaves, and sparse branching patterns. A few accessions appeared as outliers due to rare trait expressions, including obovate leaf shape and purple berry colour, which contributed strongly to their discrimination in the MCA space. Qualitative trait distribution was dominated by elliptic leaf shape (87.5%), apiculate apex (81.25%), and red berry colour (41.67%). Overall, these findings indicate a moderate level of phenotypic diversity among Nigerian coffee germplasm, highlighting the need to broaden the genetic base and strengthen improvement efforts in Coffea canephora. The considerable variability observed in qualitative traits further suggests that molecular-level investigations would be valuable for elucidating their genetic basis and potential application in coffee breeding programs.