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Genomic Strategies Against STB disease of wheat

Periodic Reporting for period 1 - GSAS (Genomic Strategies Against STB disease of wheat)

Reporting period: 2018-07-16 to 2020-07-15

Wheat is a primary tillage crop in Ireland and remains the most important cereal crop within the EU. Annually huge yield losses were caused by Zymoseptoria tritici, the causal agent of septoria tritici blotch (STB) disease. Under favourable condition, STB can cause up to 50% yield losses. Farmers are heavily reliant on multiple applications of fungicides throughout the cropping season, where control of STB accounting for more than 70% of annual fungicide usage in Europe, the use of which costs the sector over €1bn per annum. Furthermore, emerging resistance to fungicides and ambitions to reduce pesticide usage in Europe requires that greater emphasis is placed on identifying novel sources of resistance to STB. Identifying sources of resistance can be accelerated using marker-assisted recurrent selection strategies and/or genome-wide selection (genomic selection, GS). Experimental wheat populations such as the multi-parent advanced generation intercross (MAGIC) are a powerful resource to dissect the genetic control of agriculturally important traits. The overall goal of this action was to harness novel sources of resistance to STB that may help reduce dependence on fungicides. . In the present study, the NIAB Diverse MAGIC (NDM) population, comprising of more than 500 recombinant inbred lines (RILs) derived from sixteen founder varieties released between 1935-2004 was investigated for STB resistance under high disease pressure environments. Genomic regions associated with resistance were identified and the linked genetic markers may support rapid selection of favorable alleles for the breeding of new wheat cultivars with improved STB resistance.
NDM population and founders were evaluated for resistance to STB at the seedling and adult plant stage in a glasshouse and two field locations in Ireland to further elucidate the complex genetic architecture underlying resistance. Plant height and heading date data were also collected to dissect epistatic interactions with STB.. The population mean for STB infection was 38.45% in the seedling experiment, and the population mean for STB infection was 66.4% in the adult plant glasshouse experiment In the field trials at Carlow and Waterford the population mean was 5.8 on a 1-9 disease rating scale. The sixteen NDM founders showed variable levels of STB severity in different experiments. The phenotypic data collected in the action was used for Quantitative trait loci (QTL) mapping analysis using available genotype data on the NDM population and founders. Phenotypic data, genotypic data, pedigree information, covariate data (i.e. plant height and flowering time data for only field experiments), and a genetic map were used for QTL mapping. QTL analysis revealed genomic regions associated with STB resistance within and across experiments. QTL were either co-located with previously reported QTL or represent new loci underpinning STB resistance.. All findings and data from this action are available via open access publication and according to FAIR principles.
The research in this action generated STB phenotypic data sets for the NIAB Diverse MAGIC population in a typically high disease pressure environment (Ireland) and supplemented this with experiments in controlled environments against different Z. tritici isolates. While QTL analysis detected genomic regions previously associated with STB resistance, we also identified new loci linked to STB resistance in these environments. Genetic markers linked with these newly identified loci are now available for further use in breeding novel cultivars with improved STB resistance, and for deployment in combination with previously reported STB resistance genes to develop lines with durable resistance. It is expected that breeding of new lines with durable resistance will greatly facilitate a reduction in pesticide usage; thereby improving the sustainability of wheat production in Europe.