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Expression and Effectiveness of Resistance in Wheat to Septoria Leaf Blotch. Gregory Shaner, Associate Professor, Department of Botany and Plant Pathology, Purdue University, West Lafayette, Indiana 47907; Robert E. Finney(2), and Fred L. Patterson(3). (2)Research Associate, Department of Botany and Plant Pathology, Purdue University, West Lafayette, Indiana 47907; (3)Professor, Department of Agronomy, Purdue University, West Lafayette, Indiana 47907. Phytopathology 65:761-766. Accepted for publication 4 February 1975. DOI: 10.1094/Phyto-65-761.

During 1973 and 1974 we evaluated wheat cultivars and breeding lines in severe epidemics of Septoria leaf blotch. We recognized two types of resistance. One, derived from the wheat cultivar Bulgaria 88, greatly reduced the number of pycnidia produced by the pathogen. The other, which apparently does not derive from any single cultivar, reduced the rate of disease development without greatly reducing the number of pycnidia. This resistance was expressed to a greater degree in later-maturing wheats. The expression of resistance derived from Bulgaria 88 was less affected by maturity. Leaf blotch severity was greater the earlier wheat was sown, on both resistant and susceptible lines. Resistance derived from Bulgaria 88 increase yields 10-20%. We are now attempting to combine the two types of resistance to achieve a higher level of disease control.