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Partial Resistance to Septoria Tritici Blotch (Mycosphaerella graminicola) in Wheat Cultivars Arina and Riband

First author: Disease and Stress Biology Department, John Innes Centre, Norwich Research Park, Colney, Norwich NR4 7UH, UK and ENSAT, Laboratoire de Biologie et Amélioration des Plantes, Avenue de l'Agrobiopole, BP107, 31326 Castanet-Tolosan, France; second and fourth authors: Disease and Stress Biology Department, John Innes Centre, Norwich UK; and third author: Advanta Seeds UK Ltd., Station Road, Docking, King's Lynn, Norfolk PE31 8LS, UK

Partial resistance to Septoria tritici blotch (STB) and its inheritance were investigated in a doubled-haploid population of a cross between cvs. Arina and Riband. The former has good partial resistance whereas the latter is susceptible. In adult plant trials in polytunnels, STB disease scores were negatively correlated with heading date. Resistance was not specific to any of the three fungal isolates used in these tests. A quantitative trait locus (QTL) for partial resistance to STB was identified in Riband on chromosome 6B and is named QStb.psr-6B-1. No QTL controlling a major part of the Arina resistance was identified, suggesting that its resistance may be dispersed and polygenic. There was no correlation between the lines' mean disease scores at the seedling and adult stages, implying that partial resistance to STB is developmentally regulated. Seedling resistance to the isolate IPO323 was isolate-specific and controlled by a single gene in Arina, probably allelic with the Stb6 gene in cv. Flame that confers resistance to the same isolate. The implications of these results for wheat breeding programs are discussed.