Comparison of Three Methods to Assess Resistance in Sunflower to Basal Stem Rot Caused by Sclerotinia sclerotiorum and S. minor.. F. S. Sedun, Department of Botany, University of New England, Armidale, N. S. W., Australia 2351. J. F. Brown, Department of Botany, University of New England, Armidale, N. S. W., Australia 2351. Plant Dis. 73:52-55. Accepted for publication 3 August 1988. Copyright 1989 The American Phytopathological Society. DOI: 10.1094/PD-73-0052.

Laboratory and field experiments assessed the relative resistance of sunflower lines to diseases caused by Sclerotinia sclerotiorum and S. minor. Resistance was measured in terms of the percentage of plants that developed disease symptoms, the time after inoculation when wilting and basal stem lesions became apparent, and the linear rate of lesion development. The linear rate of lesion development of basal stem lesions was considered to be a good measure of relative resistance to basal stem rots under laboratory and field conditions because lines with a high rate of lesion enlargement had a high incidence of basal stem lesions under field conditions and vice versa. The ranking of sunflower lines for disease resistance was similar for both S. sclerotiorum and S. minor.