Relationships between phenolics-conjugated polyamines and sensitivity of sugarcane to smut (Ustilago scitaminea)

Infection of sugarcane buds (var. Barbados 42231) with teliospores of Ustilago scitaminea changes the pattern of polyamine conjugation in several organs of 2-month-old plants. Stalks of infected plants contain SH-spermidine that does not occur in the healthy organ. Similar results have been obtained for SH-spermine in the first expanded leaf and in the stem. The amount of SH-cadaverine in the first expanded leaf, roots and stem of infected plants is always higher than that found for healthy plants. Some phenolics are also associated with different polyamine fractions. So, the amount of p-hydroxybenzoic acid in both SH and PH fractions of polyamines extracted from the root increases after infection. Syringic acid is the main phenol associated with the PH fraction in the first expanded leaf of infected plants, whereas this phenol is mainly associated with both SH and PH fractions isolated from the stem and the whip. Infection enhances conjugation of p-coumaric acid to PH polyamines, whereas caffeic acid appears in the SH fraction in leaf, root and stem. However, ferulic acid seems to be the main hydroxycinnamic acid derivative in the whip. Chlorogenic acid is associated with the SH fraction from the stem of healthy plants although this changes to free phenolics after infection.