Resistance of (Aegilops tauschii × Secale cereale) × Triticosecale Hybrids to Leaf Rust (Puccinia triticina) Determined on the Macroscopic and Microscopic Level.

Maciej Majka,Albrecht Serfling,Frank Ordon,Paweł Czembor,Halina Wiśniewska,Aurelia Ślusarkiewicz-Jarzina,Michał Tomasz Kwiatek

doi:10.3389/fpls.2018.01418

Abstract

Leaf rust caused by Puccinia triticina Eriks belongs to the most important fungal pathogens of wheat (Triticum aestivum L.) and triticale (× Triticosecale). Effective resistance to leaf rust is both, cost-effective and environmentally safe. Many wild Aegilops species carry unknown resistances against fungal diseases and are characterized by a high genetic variability. The main goal of this work was to examine the resistance of (Aegilops tauschii × Secale cereale) × Triticosecale hybrids to leaf rust in inoculation tests with different races of P. triticina. Hybrid plants were selected for the presence of 2D chromosome/s in the triticale background using fluorescence and genomic in situ hybridization. The presence of leaf rust resistance genes was confirmed with closely linked molecular markers, i.e., Xgdm35 and Xgwm296. 14 genotypes of BC2F4 – BC2F6 hybrid plants with the monosomic addition of chromosome 2D (M2DA) were analyzed together with nine control lines. Resistance was determined at the macroscopic and microscopic level at the seedling and adult plant stage (flag leaf). In general, results revealed limited resistance of hybrid plants at the seedling stage, followed by an increase of the resistance level at later stages of plant development. This indicates that respective hybrid plants may exhibit APR resistance conferred by Lr22a introgressed from Ae. tauschii. On the basis of the macroscopic and microscopic analysis, this kind of resistance turned out to be additive and race-specific. We selected four monosomic 2D addition triticale genotypes highly resistant to P. triticina infection at the two main stages of plant development. From the selected genotypes, we obtained 26 doubled haploid lines among which two lines with doubled additional chromosomes 2D of Ae. tauschii can be used for further breeding to increase leaf rust resistance of cultivated triticale.

Highlights

Leaf rust caused by Puccinia triticina Eriks, is one of the most destructive and important foliar diseases of cereals, especially because of the wide distribution and potential to develop rapidly under optimal environmental conditions (Kolmer, 1996; Dean et al, 2012; Chen et al, 2013)
Because of the diversity of genes and according to previous results (Majka et al, 2016), hybrid plants were selected for the presence of 2D chromosome/s in triticale background
Obtained results revealed that hybrids and control plants at the adult plant stage were less infected than seedlings in case of isolates 1 and 2, whereas after inoculation with isolate 1 we identified no infection on the hybrid plants (Supplementary Table S1 and Figure 5)

Summary

Introduction

Leaf rust caused by Puccinia triticina Eriks, is one of the most destructive and important foliar diseases of cereals, especially because of the wide distribution and potential to develop rapidly under optimal environmental conditions (Kolmer, 1996; Dean et al, 2012; Chen et al, 2013). In order to avoid yield losses and reduced quality, host resistance is both cost-effective and environmentally safe (Assefa and Fehrmann, 2000; Kalia et al, 2017). Genetic resistance to leaf rust can be determined as seedling resistance or adult plant resistance (APR). The APR is described as a susceptible reaction at the seedling stage, followed by an increased level of resistance in further stages of plant development. APR can be either race-specific (e.g., Lr12) or race-non-specific (e.g., Lr34) and is usually measured on the flag leaf (Dyck and Kerber, 1985; Park and McIntosh, 1994; McIntosh et al, 1995)

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