Loci on chromosomes 1A and 2A affect resistance to tan (yellow) spot in wheat populations not segregating for tsn1

Manisha Shankar,Grant J Hollaway,Rebecca Fox,Mark S Mclean,Dorthe Jorgensen,Stephen M Neate,Julian Taylor,Ken J Chalmers,Hossein Golzar,Robert Loughman,Elysia Vassos,Diane E Mather

doi:10.1007/s00122-017-2981-6

Abstract

Key messageQTL for tan spot resistance were mapped on wheat chromosomes 1A and 2A. Lines were developed with resistance alleles at these loci and at the tsn1 locus on chromosome 5B. These lines expressed significantly higher resistance than the parent withtsn1only.Tan spot (syn. yellow spot and yellow leaf spot) caused by Pyrenophora tritici-repentis is an important foliar disease of wheat in Australia. Few resistance genes have been mapped in Australian germplasm and only one, known as tsn1 located on chromosome 5B, is known in Australian breeding programs. This gene confers insensitivity to the fungal effector ToxA. The main aim of this study was to map novel resistance loci in two populations: Calingiri/Wyalkatchem, which is fixed for the ToxA-insensitivity allele tsn1, and IGW2574/Annuello, which is fixed for the ToxA-sensitivity allele Tsn1. A second aim was to combine new loci with tsn1 to develop lines with improved resistance. Tan spot severity was evaluated at various growth stages and in multiple environments. Symptom severity traits exhibited quantitative variation. The most significant quantitative trait loci (QTL) were detected on chromosomes 2A and 1A. The QTL on 2A explained up to 29.2% of the genotypic variation in the Calingiri/Wyalkatchem population with the resistance allele contributed by Wyalkatchem. The QTL on 1A explained up to 28.1% of the genotypic variation in the IGW2574/Annuello population with the resistance allele contributed by Annuello. The resistance alleles at both QTL were successfully combined with tsn1 to develop lines that express significantly better resistance at both seedling and adult plant stages than Calingiri which has tsn1 only.

Highlights

Tan spot caused by the fungus Pyrenophora tritici-repentis (Died.) Drechs. [anamorph Drechslera tritici-repentis (Died.) Shoem.] is an important foliar disease of bread wheat (Triticum aestivum L.) and durum wheat (T. turgidum L. var. durum)
In the field trials, the error term consisted of a residual variance as well as a correlation structure parameterized as a separable AR1 × AR1 (AR1 = auto-regressive process of order 1) that models the dependency of the observations due to the proximity of neighbouring plots in the experiment
In the field experiments conducted at South Perth, heritability estimates were very high for Zadoks growth stage assessed at 12 weeks (2009: 0.93 for Calingiri/Wyalkatchem and 0.89 for IGW2574/Annuello) and days to heading (2010: 0.97 in Calingiri/Wyalkatchem and 0.91 in IGW2574/Annuello)

Summary

Introduction

Tan spot (syn. yellow spot and yellow leaf spot) caused by the fungus Pyrenophora tritici-repentis (Died.) Drechs. [anamorph Drechslera tritici-repentis (Died.) Shoem.] is an important foliar disease of bread wheat (Triticum aestivum L.) and durum wheat (T. turgidum L. var. durum). [anamorph Drechslera tritici-repentis (Died.) Shoem.] is an important foliar disease of bread wheat (Triticum aestivum L.) and durum wheat It was first identified in the United States in the 1940s, and since has increased in incidence and severity worldwide (Wolf et al 1998; Ciuffetti and Tuori 1999). Wheat can be infected by P. tritici-repentis at any developmental stage, with disease perpetuation during crop maturity and grain filling having the greatest impact on grain quality and yield (Bankina and Priekule 2011). Where wet conditions are present during grain filling, the disease can progress to severe levels (Ronis and Semaskiene 2006) and cause yield losses between 20 and 50% as observed in Queensland and Western Australia (Shipton 1968; Rees et al 1982; Rees and Platz 1983; Bhathal et al 2003)

Objectives

Methods

Results

Conclusion