J. Hakulinen et al., Leaf phenolics of three willow clones differing in resistance to Melampsora rust infection, PHYSL PLANT, 105(4), 1999, pp. 662-669
Leaf phenolic composition in three Salix myrsinifolia Salisb, clones (V8, V
45, and V43), inoculated with Melampsora rust, was analyzed to detect local
rust-induced alterations during different stages of infection (2, 7, and 2
1 days after inoculation [DAI]). Phenolic levels and percentage of uredial
area varied significantly between clones, In the most resistant clone,V8, t
he levels of some phenolic compounds were lower in rust-infected plants tha
n in control plants at the initial stages of rust infection, suggesting a r
apid 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 p
henolics at 7 DAI, This: increase may have been effective in retarding the
subsequent spread and development of rust, In the most susceptible clone V4
3, rust-induced phenolic responses were less pronounced and delayed. The re
sults suggest that in specific willow-rust interactions, constitutive level
s of phenolics, as well as induced phenolic responses, may contribute to th
e expression of rust resistance. In general, rust-induced alterations in wi
llow phenolic levels are highly specific to genotype and compound and vary
depending on the stage of rust development.