Defence responses including hypersensitive cell death, oxidative burst and defence gene expression in Moro wheat inoculated with Puccinia striiformis

This study integrated defence-related gene profiling with histological and histochemical observations to develop a detailed time-course description of Puccinia striiformis penetration and infection of susceptible Fielder wheat and resistant Moro that contains the Yr10 gene for stripe rust resistance. Penetration and establishment events of the pathogen within the leaf were very similar in both Fielder and Moro until approximately 8-12 days after inoculation (dai). Two oxidative bursts, one at 6 dai and a second at 14 dai, were recorded. Early mild up-regulation of the defence signalling genes associated with jasmonic acid pathway EDS1, PAD4 and AOS were observed as early as 4 days after inoculation (dai) in Moro compared with Fielder. Transcripts of PR1.1, a gene associated with the salicylic acid pathway, and of a thaumatin-like protein, were differentially up-regulated from 6 to 12 dai in Moro compared with Fielder. A toxic response in fungal tissues was observed coincident with the hypersensitive response (HR) in Moro that terminated further growth of the pathogen. The anatomical and cytological aspects of defence expression are discussed in relation to profiling of different defence genes. © 2014 The Canadian Phytopathological Society.