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

Adnan Riaz,James Cockram,James Gerard Hehir,Dan Milbourne,Stephen Byrne,Jie Kang,John Spink,Fergus Meade,Petra Kockappelgren,Ewen Mullins

doi:10.3390/genes11080887

Abstract

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.

Highlights

Bread or common wheat (Triticum aestivum L.) is a primary tillage crop in Ireland and the most important cereal crop in the European Union (EU), accounting for 46% of EU-28 cereal production [1].Annual wheat yield losses are observed due to extreme weather patterns such as heat, heavy rainfall, drought, and nutrient deficiency [2,3]
The polycyclic pycnidiospores are dispersed by rain-splash, helping to propagate septoria tritici blotch (STB) epidemics through the wheat growing season [15,16]
The progress of an STB epidemic depends on the availability of optimal temperature (22 ◦ C) [17] and relative humidity (≥85%) [18], which promotes the appearance of black asexual fruiting bodies that in turn disperse pycnidiospores from infected leaves [19]

Summary

Introduction

Bread or common wheat (Triticum aestivum L.) is a primary tillage crop in Ireland and the most important cereal crop in the European Union (EU), accounting for 46% of EU-28 cereal production [1].Annual wheat yield losses are observed due to extreme weather patterns such as heat, heavy rainfall, drought, and nutrient deficiency [2,3]. STB epidemics can cause a yield loss of up to 50% in fields when a susceptible wheat cultivar is grown [8,9]. Z. tritici produces ascospores and pycnidiospores via a sexual [12] and an asexual life cycle [13], respectively. Both types of spores can serve as primary inoculum depending upon environmental conditions, cropping history, and management [14]. The progress of an STB epidemic depends on the availability of optimal temperature (22 ◦ C) [17] and relative humidity (≥85%) [18], which promotes the appearance of black asexual fruiting bodies (pycnidia) that in turn disperse pycnidiospores from infected leaves [19]

Methods

Results

Conclusion