• Genetic Analysis Using a Multi-Parent Wheat Population Identifies Novel Sources of Septoria Tritici Blotch Resistance

      Riaz, Adnan; KockAppelgren, Petra; Hehir, James Gerard; Kang, Jie; Meade, Fergus; Cockram, James; Milbourne, Dan; Spink, John; Mullins, Ewen; Byrne, Stephen; et al. (MDPI AG, 2020-08-04)
      Zymoseptoria tritici is the causative fungal pathogen of septoria tritici blotch (STB) disease of wheat (Triticum aestivum L.) that continuously threatens wheat crops in Ireland and throughout Europe. Under favorable conditions, STB can cause up to 50% yield losses if left untreated. STB is commonly controlled with fungicides; however, a combination of Z. tritici populations developing fungicide resistance and increased restrictions on fungicide use in the EU has led to farmers relying on fewer active substances. Consequently, this serves to drive the emergence of Z. tritici resistance against the remaining chemistries. In response, the use of resistant wheat varieties provides a more sustainable disease management strategy. However, the number of varieties offering an adequate level of resistance against STB is limited. Therefore, new sources of resistance or improved stacking of existing resistance loci are needed to develop varieties with superior agronomic performance. Here, we identified quantitative trait loci (QTL) for STB resistance in the eight-founder “NIAB Elite MAGIC” winter wheat population. The population was screened for STB response in the field under natural infection for three seasons from 2016 to 2018. Twenty-five QTL associated with STB resistance were identified in total. QTL either co-located with previously reported QTL or represent new loci underpinning STB resistance. The genomic regions identified and the linked genetic markers serve as useful resources for STB resistance breeding, supporting rapid selection of favorable alleles for the breeding of new wheat cultivars with improved STB resistance.
    • Temporal and spatial field evaluations highlight the importance of the presymptomatic phase in supporting strong partial resistance in Triticum aestivum against Zymoseptoria tritici

      Hehir, J. G.; Connolly, C.; O'Driscoll, A.; Lynch, J. P.; Spink, John; Brown, J. K. M.; Doohan, F.; Mullins, Ewen; Department of Agriculture, Food and the Marine; RSF 11S121; et al. (Wiley, 2017-11-24)
      Zymoseptoria tritici, the causal agent of septoria tritici blotch (STB), remains a significant threat to European wheat production with the continuous emergence of fungicide resistance in Z. tritici strains eroding the economic sustainability of wheat production systems. The life cycle of Z. tritici is characterized by a presymptomatic phase (latent period, LP) after which the pathogen switches to an aggressive necrotrophic stage, when lesions bearing pycnidia quickly manifest on the leaf. As minimal knowledge of the possible role of the LP in supporting STB resistance/susceptibility exists, the goal of this study was to investigate the spatial and temporal association between the LP and disease progression across three locations (Ireland – Waterford, Carlow; UK – Norwich) that represent commercially high, medium and low STB pressure environments. Completed over two seasons (2013–2015) with commercially grown cultivars, the potential of the LP in stalling STB epidemics was significant as identified with cv. Stigg, whose high level of partial resistance was characterized by a lengthened LP (c. 36 days) under the high disease pressure environment of Waterford. However, once the LP concluded it was followed by a rate of disease progression in cv. Stigg that was comparable to that observed in the more susceptible commercial varieties. Complementary analysis, via logistic modelling of intensive disease assessments made at Carlow and Waterford in 2015, further highlighted the value of a lengthened LP in supporting strong partial resistance against STB disease of wheat.