Hakulinen J, Sorjonen S, Julkunen-Tiitto R
Leaf phenolics of three willow clones differing in resistance to Melampsora rust infection
Physiologia Plantarum: 1999 105:662-669
Leaf phenolic composition in three Salix myrsinifolia Salisb, clones (V8, V45, and V43), inoculated with Melampsora rust, was analyzed to detect local rust-induced alterations during different stages of infection (2, 7, and 21 days after inoculation [DAI]). Phenolic levels and percentage of uredial area varied significantly between clones, In the most resistant clone,V8, the levels of some phenolic compounds were lower in rust-infected plants than in control plants at the initial stages of rust infection, suggesting a rapid response of phenolic metabolism to rust attack. Moreover, the clone V8 contained the highest constitutive (+)-catechin level, In clone V45, rust infection caused the most pronounced increase in the levels of individual phenolics at 7 DAI, This: increase may have been effective in retarding the subsequent spread and development of rust, In the most susceptible clone V43, rust-induced phenolic responses were less pronounced and delayed. The results suggest that in specific willow-rust interactions, constitutive levels of phenolics, as well as induced phenolic responses, may contribute to the expression of rust resistance. In general, rust-induced alterations in willow phenolic levels are highly specific to genotype and compound and vary depending on the stage of rust development.
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