The relationship between graft incompatibility and phenols in Uapaca kirkiana Müell Arg.

The objective of the study was to determine the relationship between phenols and graft incompatibility in Uapaca kirkiana. Phenol quantification and identification were carried out using Folin-Ciocalteau reagent procedure, fluorescence microscopy and reverse phase high performance liquid chromatograph (RP-HPLC) above, below and at the graft union. Results showed no vascular cambium continuity above the scion/stock unions. Significant differences in total soluble phenols and cell wall bound phenols were obtained. Fluorescence microscope indicated the presence of flavonoids and other polymers above the union. The RP-HPLC identified ferulic acid as a major phenol component found in U. kirkiana plant cells and responsible for wood discolouration. High phenol concentrations were obtained in less compatible combinations than in compatible combinations. High peaks of ρ-coumaric acid were obtained above the union. It is concluded that phenols, especially ρ-coumaric acids and flavonoids caused poor callus formation at the union, and hence implicated in graft incompatibility.