The Content of Phenolic Compounds and the Activity of Key Enzymes of Their Synthesis in Scots Pine Hypocotyls Infected with Fusarium

Twelve-day-old seedlings of Scots pine (Pinus sylvestris L.) were infected with a virulent spore suspension of the fungus Fusarium sporotrichiella var. sporotrichioides Bilai. 72 h after infection, the seedlings were divided into infection-susceptible and infection-resistant ones, and phenolic compounds in the seedling hypocotyls were analyzed. Susceptible seedlings contained 4.3-fold less lignins, 1.4-fold less free and bound proanthocyanidins, 12.7-fold less free hydroxybenzoic acids, 56.6-fold less bound hydroxybenzoic acids, 2-fold less quinic acid, and 5.1-fold less shikimic acid as compared to the resistant seedlings. At the same time, L-phenylalanine content was increased 3-fold and that of L-tyrosine, 1.3-fold. The activity of quinate:NAD(P)⁺ oxidoreductase and L-phenylalanine ammonia-lyase in the hypocotyls of susceptible seedlings was 2.3-fold and 1.4-fold lower, respectively, whereas the activity of shikimate:NAD(P)⁺ oxidoreductase remained unchanged.