|Variability in virulence as determined by honeydew production by strains of Claviceps purpurea (Fr.) Tul. on eight genotypes of wheat.|
J. MENZIES (1), A. Gordon (2), D. O'Sullivan (3). (1) Agriculture and Agri-Food Canada, Morden, MB, Canada; (2) National Institute of Agricultural Botany, Cambridge, United Kingdom; (3) University of Reading, Reading, United Kingdom
Ergot, caused by <i>Claviceps purpurea</i> has steadily increased in incidence and severity on the Canadian prairies since 1999. The development of resistant wheat lines is being explored. The variability in pathogenicity among strains of <i>C. purpurea</i> in nature is not known. The objective of this work was to study variability in pathogenicity among different strains of <i>C. purpurea</i> for honeydew production on wheat lines differing in levels of resistance. Forty seven pathogen strains from the Canadian prairies and the United Kingdom were inoculated onto 3 durum wheat (<i>Triticum aestivum</i> L. var. <i>durum</i>) lines (‘Melita’, ‘Kyle’, and 9260B-173A) and 5 hexaploid wheat (<i>T. aestivum</i>) lines (‘Cadillac’’, ‘Vista’, ‘Kenya Farmer’, ‘Lee’, and HY630). Nine spikes per wheat line were needle inoculated prior to anthesis for each pathogen strain using a conidial suspension. Each spike was assessed for honeydew production 14 days after inoculation using a scale of 1 to 4; 1=no honeydew visible, 2=honeydew confined within glumes, 3=honeydew exuding from florets in small drops, and 4=large drops of honeydew running down the spike. There were significant differences among the 8 wheat genotypes for the mean honeydew production. Pathogen strains were considered to be virulent when they produced a honeydew rating of 2.5 or higher. Different virulence phenotypes were identified, and there was a wide range of genetic variability among strains of <i>C. purpurea</i>.