Detection of small-effect QTL associated with the resistance to Septoria nodorum blotch in a hexaploid winter wheat population

Authors: RIVERA BURGOS, LUIS - North Carolina State University; Brown-Guedira, Gina; JOHNSON, JERRY - University Of Georgia; MERGOUM, MOHAMED - University Of Georgia; Cowger, Christina

Submitted to: PLOS ONE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/30/2022
Publication Date: 5/19/2022
Citation: Rivera Burgos, L., Brown Guedira, G.L., Johnson, J., Mergoum, M., Cowger, C. 2022. Detection of small-effect QTL associated with the resistance to Septoria nodorum blotch in a hexaploid winter wheat population. PLoS ONE. 8546. https://doi.org/10.1371/journal.pone.0268546.
DOI: https://doi.org/10.1371/journal.pone.0268546

Interpretive Summary: In humid and temperate areas, Septoria nodorum blotch (SNB) is a major fungal disease of common wheat (Triticum aestivum L.) in which grain yield is reduced when the pathogen, Parastagonospora nodorum, infects leaves and glumes during grain filling. Foliar SNB susceptibility may be associated with sensitivity to P. nodorum necrotrophic effectors (NEs). Both foliar and glume susceptibility are quantitative, and the underlying genetics are not understood in detail. We genetically mapped resistance quantitative trait loci (QTL) to leaf and glume blotch using a double haploid (DH) population derived from the cross between the moderately susceptible cultivar AGS2033 and the resistant breeding line GA03185-12LE29. The population was evaluated for SNB resistance in the field in four successive years (2018–2021). We identified major heading date (HD) and plant height (PH) variants on chromosomes 2A and 2D, co-located with SNB escape mechanisms. Five QTL with small effects associated with adult plant resistance to SNB leaf and glume blotch were detected on 1A, 1B, and 6B linkage groups. These QTL explained a relatively small proportion of the total phenotypic variation, ranging from 5.6 to 11.8%. The small-effect QTL detected in this study did not overlap with QTL associated with morphological and developmental traits, and thus are sources of resistance to SNB.

Technical Abstract: In humid and temperate areas, Septoria nodorum blotch (SNB) is a major fungal disease of common wheat (Triticum aestivum L.) in which grain yield is reduced when the pathogen, Parastagonospora nodorum, infects leaves and glumes during grain filling. Leaf SNB susceptibility is partly explained by sensitivity to corresponding P. nodorum necrotrophic effectors (NEs). Glume SNB susceptibility is also quantitative; however, the underlying genetics are not understood in detail. We genetically mapped resistance quantitative trait loci (QTL) to leaf and glume blotch using a double haploid (DH) population derived from the cross between the moderately susceptible cultivar AGS2033 and the resistant breeding line GA03185-12LE29. The population was evaluated for SNB resistance in the field in four successive years (2018-2021). We identified major heading date (HD) and plant height (PH) variants in chromosome 2A and 2D, co-located with SNB outbreak escape mechanisms. Five QTL with small effects associated with SNB leaf and glume adult plant resistance were detected on 1A, 1B, and 6B linkage groups. These QTL explained a relatively small proportion of the total phenotypic variation, ranging from 5.6 to 11.8%. The small-effect QTL detected in our study did not overlap with QTL associated with morphological and developmental traits; thus, they could be involved in the defense reaction.