Ra. Plowright et al., THE INDUCTION OF PHENOLIC-COMPOUNDS IN RICE AFTER INFECTION BY THE STEM NEMATODE DITYLENCHUS-ANGUSTUS, Nematologica, 42(5), 1996, pp. 564-578
Changes in the phenolic profiles of five resistant and two suspectible
varieties of deep water rice were examined following infection by the
rice stem nematode Ditylenchus angustus. Within resistant cultivars,
inoculated plants were either symptomless or exhibited symptoms of inc
ompatible (resistant), compatible (suspectible) or partially compatibl
e responses. Extracts of leaf tissues from inoculated and uninoculated
plants were made in methanol (80% v/v) and analysed by reverse phase
HPLC. Tissues from inoculated plants with and without symptoms were ex
amined separately Traces revealed the presence of 13 to 18 UV absorbin
g constituents of rice leaf extracts, depending on the variety. Chloro
genic acid occurred in small amounts and only in resistant plants, but
there was no correlation between constitutive compounds and resistanc
e or susceptibility. The secondary chemistry of tissues exhibiting sym
ptoms changed in all resistant varieties. Levels of chlorogenic acid i
ncreased in response to infection. Furthermore in two resistant select
ions of rice variety Rayada 16-06, a newly formed compound, the rice p
hytoalexin sakuranetin was also isolated. There was correlative eviden
ce that both of these compounds could have a functional role in resist
ance. At 5 days after inoculation the concentrations of sakuranetin in
Rayada 16-06 were 8 & 13 mu g/g leaf in plants with 10 and 200 D. ang
ustus/plant, respectively No change in secondary chemistry occurred in
susceptible varieties.