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Phenylalanine Ammonia-lyase, Tyrosine Ammonia-lyase, and Lignin in Wheat Inoculated with Erysiphe graminis f. sp. tritici. Norman E. Green, Research Technologist, Department of Plant Pathology, Washington State University, Pullman 99163; Lee A. Hadwiger(2), and Shirl O. Graham(3). (2)(3)Professors, Department of Plant Pathology, Washington State University, Pullman 99163. Phytopathology 65:1071-1074. Accepted for publication 18 April 1975. DOI: 10.1094/Phyto-65-1071.

The host-parasite response of an Erysiphe graminis f. sp. tritici race 21 (avirulent to Pm1, Pm2, Pm3a, Pm3b, and Pm4 genotypes)-inoculated isoline of wheat containing the Pm2 gene was distinguishable from responses of inoculated pmx, Pm1, Pm3a, Pm3b, and Pm4 isolines on the basis of lignin accumulation and level of phenylalanine ammonia-lyase (PAL). Phenylalanine ammonia-lyase (PAL) and tyrosine ammonia-lyase (TAL) activity increased significantly in all inoculated genotypes beginning 4 hours after inoculation, reached a peak at 24 hours after inoculation, and then decreased sharply by 48 hours after inoculation. More than twofold increases in PAL were noted at 4 hours after inoculation, which is prior to the time of appressorial development. In the inoculated Pm2 genotype, the OAL and TAL activity again increased sharply beyond 48 hours, and reached a maximum 96 hours after inoculation. Beyond 48 hours after inoculation, all other inoculated genotypes which were assayed continued to decrease in PAL and TAL activity to levels near that of the noninoculated controls. The isoline containing the Pm2 gene was the only isoline in which an accumulation of lignin could be detected histochemically 92 hours after inoculation.

Additional keywords: disease resistance, powdery mildew, isolines.