International Symposium on Cereal Leaf Blights 2019 | University College Dublin, Ireland | 22-24 May 2019

Long-term screening of winter wheat cultivars for Septoria nodorum blotch resistance

Christina Cowger*

Brian Ward
North Carolina State University

James K. M. Brown
John Innes Centre

Gina Brown-Guedira

Oral Presentation
Host Genetics and Resistance Breeding

Moore Auditorium, UCD O'Brien centre for Science
23 May 2019, 16:40

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Between 2009 and 2018, 2,161 winter wheat genotypes were tested as part of an ongoing US screening program to increase resistance to Septoria nodorum blotch (SNB), caused by Parastagonospora nodorum.  The genotypes were mainly advanced experimental lines from 21 public and private breeding programs in the central and eastern US.  Replicated trials were performed in 16 year*location environments (one or two environments per year) at public research stations in North Carolina, US.  Plots were inoculated with P. nodorum-infected straw at about Zadoks growth stage 28.  Irrigation was provided in some environments to ensure adequate disease development.  Whole-plot disease ratings were on a 1-9 scale, with 1 the lowest and 9 the highest possible level of disease.  While experimental lines were usually in the nursery fewer than 3 years, some commercial varieties were tested longer.  To assess durability of quantitative resistance (QR) to SNB, a linear mixed model was fitted to data from the 19 genotypes that each appeared at least 7 years in the trials, plus one genotype that was tested 6 years and is known to possess quantitative resistance (QR) to several diseases.  While mean levels of foliar and glume SNB increased significantly in the nursery over the period (P < 0.002), there was only weak evidence for variation in the rate at which foliar SNB changed on different varieties (P = 0.06), and no such evidence with regard to glume SNB, demonstrating durability of the QR in this germplasm. Of the 2,161 wheat genotypes phenotyped during that period, genotyping-by-sequencing data were available for 1,233.  A mixed-model genome-wide association study was performed using data for those lines, and results of the study will be presented.