Towards a minimum number of key flower traits in studies of Coffea spp. phenotype variability

•Flower morphological traits can be used to differentiate Coffea spp. genotypes.•Among nine flower traits, four are explaining 70.8 % of the variation.•Floral trait evaluation was optimized by eliminating five of nine traits.•Some flower morphological traits of flowers in Coffea spp. are correlated.•Some C. canephora genotypes have flowers morphologically similar to C. arabica. The identification of key traits in optimization of phenotypic variability studies represents time savings in development of new cultivars. To attain this purpose, it was hypothesized that: 1) different coffee genotypes presented morphological variability in flower size and form, 2) various coffee flower size and form traits were correlated, 3) the exclusion of correlated flower morphological traits can facilitate future flower evaluations, without compromising the inference of phenotypic variability. A total of 36 Coffea canephora and the two C. arabica genotypes were studied. Nine floral traits were measured in 760 flowers. It was proven that the flower phenology can be used to differentiate Coffea spp. genotypes. Some genotypes of C. canephora, such as Beira Rio 8, Guarani, 8R, and Clementino, had the largest floral structures. On the other hand, the genotypes Z8, Verdim D, Ouro Negro 1, Tardio C, NV8, Ouro Negro 2, Bamburral, LB1, and Peneirão had the smallest floral structures. Among the nine evaluated floral traits, the five (petal length, anther length, stamen length, style length, and stigmatic lobe length) were strongly correlated with the traits of the greatest weight for data variability. The correlated traits had little contribution to the data variability, permitting that their exclusion had not compromised the inference of morphological flower variability in Coffea spp. genotypes. This suggested that studies aiming at differing the Coffea spp. genotypes based on floral structures may consider the four studied traits, tube length, tube diameter, corolla diameter, and the number of floral appendages (petals or stamens). The reduction of nine to these four traits can optimize time and efficiency in data collection. In the future works, the association of selected flower morphological traits with traits related to Coffea spp. production could additionally move ahead the process of coffee breeding programs. [Display omitted]