VIEW ARTICLE

Resistance

Papilla Formation and Hypersensitivity at Penetration Sites and Resistance to Pseudocercosporella herpotrichoides in Winter Wheat. T. D. Murray, Assistant professor, Department of Plant Pathology, Washington State University, Pullman 99164-6430; Huazhi Ye, visiting scientist, Sichuan Agricultural College, Yaan, People's Republic of China. Phytopathology 76:737-744. Accepted for publication 18 February 1986. Copyright 1986 The American Phytopathological Society. DOI: 10.1094/Phyto-76-737.

Seedlings of six winter wheat cultivars were inoculated with conidia of Pseudocercosporella herpotrichoides and the infection process followed. Penetration of coleoptiles and leaf sheaths occurred sooner in susceptible than in resistant cultivars. Lignified papillae, stain halos, and a hypersensitive reaction formed in epidermal cells in response to penetration in all cultivars. More papillae were found in first leaf sheaths of resistant than of susceptible cultivars; VPM, the most resistant cultivar, had the most papillae at penetration sites (100%) and Selection 101, the most susceptible cultivar, had the fewest papillae (66%). Fewer successful penetrations occurred in resistant than in susceptible cultivars at sites where papillae were present. However, penetration always occurred when papillae did not form, regardless of host resistance. The total number of successful penetrations (sites with and without papillae) increased with increasing host susceptibility from 2.3% in VPM to 74.3% in Selection 101. The hypersensitive reaction occurred only at sites with papillae, and there were fewer successful penetrations at sites with both papillae and the hypersensitive reaction than at sites with papillae alone in all cultivars except VPM. Histochemical tests indicated lignin was present in papillae of all cultivars. These data indicate that both lignified papillae and hypersensitive reactions are involved in seedling resistance to P. herpotrichoides.