RESISTANCE OF WHEAT TO PUCCINIA-GRAMINIS F SP TRITICI - ASSOCIATION OF THE HYPERSENSITIVE REACTION WITH THE CELLULAR ACCUMULATION OF LIGNIN-LIKE MATERIAL AND CALLOSE

Seedlings of wheat (Triticum aestivum L.) containing the Sr5 gene for resistance to wheat stem rust were inoculated with race 32 of Puccinia graminis (Pers.) f.sp. tritici Eriks. & E. Henn., which contains the corresponding P5 gene for avirulence, and primary leaves were examined microscopically for host-parasite interaction. Infected epidermal and mesophyll cells containing the Sr5 gene reacted hypersensitively, with accumulation of compounds that autofluoresce yellow during excitation with ultraviolet light. Histochemical tests for lignin using phloroglucinol and chlorinesulphite were positive in hypersensitively necrotic wheat cells. In addition, callose was localized in yellow fluorescing necrotic cells by treatment with resorcinol blue or lacmoid. Products of radiolabelled [14C]-cinnamic acid accumulated in the hypersensitively necrotic wheat cells. In vivo application of the competitive inhibitor of phenylalanine ammonia-lyase (PAL, E.C. 4.3.1.5), α-aminooxyacetate, inhibited the hypersensitive reaction and markedly altered resistance expression. The data provide evidence that the accumulation of lignin or lignin-like material is associated with the hypersensitive reaction conditioned by the Sr5 gene. © 1990.