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 incompatible (resistant), compatible (suspectible) or partially compatible 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 examined separately. Traces revealed the presence of 13 to 18 UV absorbing constituents of rice leaf extracts, depending on the variety. Chlorogenic acid occurred in small amounts and only in resistant plants, but there was no correlation between constitutive compounds and resistance or susceptibility. The secondary chemistry of tissues exhibiting symptoms changed in all resistant varieties. Levels of chlorogenic acid increased in response to infection. Furthermore in two resistant selections of rice variety Rayada 16-06, a newly formed compound, the rice phytoalexin sakuranetin was also isolated. There was correlative evidence that both of these compounds could have a functional role in resistance. At 5 days after inoculation the concentrations of sakuranetin in Rayada 16-06 were 8 & 13 µg/g leaf in plants with 10 and 200 D. angustus/plant, respectively. No change in secondary chemistry occurred in susceptible varieties.
Gill, J.R.; Grayer, R.J.; Harborne, J.B; Plowright, R.A.; Rahman, M.L. The Induction of Phenolic Compounds in Rice After Infection By the Stem Nematode Ditylenchus Angustus. Nematologica (1996) 42 (5) 564-578. [DOI: 10.1163/004625996X00063]