Anna Gordon, Curt McCartney, Ron E. Knox, Nelzo Ereful, Colin W. Hiebert, David J. Konkin, Ya-Chih Hsueh, Vijai Bhadauria, Mara Sgroi, Donal M. O’Sullivan, Caroline Hadley, Lesley A. Boyd & Jim G. Menzies

Theoretical and Applied Genetics June 2020, vol. 133:  1873–1886

Key message

Four QTL for ergot resistance (causal pathogen Claviceps purpurea) have been identified in the durum wheat cultivar Greenshank.

Abstract

Claviceps purpurea is a pathogen of grasses that infects flowers, replacing the seed with an ergot sclerotium. Ergot presents a significant problem to rye, barley and wheat, in particular hybrid seed production systems. In addition, there is evidence that the highly toxic alkaloids that accumulate within sclerotia can cross-contaminate otherwise healthy grain. Host resistance to C. purpurea is rare, few resistance loci having been identified. In this study, four ergot resistance loci are located on chromosomes 1B, 2A, 5A and 5B in the durum wheat cv. Greenshank. Ergot resistance was assessed through analysis of phenotypes associated with C. purpurea infection, namely the number of inoculated flowers that produced sclerotia, or resulted in ovary death but no sclerotia, the levels of honeydew produced, total sclerotia weight and average sclerotia weight and size per spike. Ergot testing was undertaken in Canada and the UK. A major effect QTL, QCp.aafc.DH-2A, was detected in both the Canadian and UK experiments and had a significant effect on honeydew production levels. QCp.aafc.DH-5B had the biggest influence on total sclerotia weight per spike. QCp.aafc.DH-1B was only detected in the Canadian experiments and QCp.aafc.DH-5A in the UK experiment. An RNASeq analysis, undertaken to identify wheat differentially expressed genes associated with different combinations of the four ergot resistance QTL, revealed a disproportionate number of DEGs locating to the QCp.aafc.DH-1B, QCp.aafc.DH-2A and QCp.aafc.DH-5B QTL intervals.

See https://link.springer.com/article/10.1007/s00122-020-03561-9

Figure 3: Ergot resistance QTL identified in the Greenshank_RIL3 × AC Avonlea DH population. Four QTL were identified using phenotypic data for HD—honeydew production level, TW—total sclerotia weight, SW—average sclerotia weight, SS—average sclerotia size per spike,  %Inf—the percentage of Claviceps purpurea inoculated flowers that developed a sclerotia, and  %Zero—the percentage of C. purpurea inoculated flowers that did not develop sclerotia, but were left with a dried-out ovary