Abstract
The hexaploid spring wheat cultivar, Carberry, was registered in Canada in 2009, and has since been grown over an extensive area on the Canadian Prairies. Carberry has maintained a very high level of leaf rust (Puccinia triticina Eriks.) resistance since its release. To understand the genetic basis of Carberry’s leaf rust resistance, Carberry was crossed with the susceptible cultivar, Thatcher, and a doubled haploid (DH) population of 297 lines was generated. The DH population was evaluated for leaf rust in seven field environments at the adult plant stage. Seedling and adult plant resistance (APR) to multiple virulence phenotypes of P. triticina was evaluated on the parents and the progeny population in controlled greenhouse studies. The population was genotyped with the wheat 90 K iSelect single nucleotide polymorphism (SNP) array, and quantitative trait loci (QTL) analysis was performed. The analysis using field leaf rust response indicated that Carberry contributed nine QTL located on chromosomes 1B, 2B (2 loci), 2D, 4A, 4B, 5A, 5B, and 7D. The QTL located on 1B, 2B, 5B, and 7D chromosomes were observed in two or more environments, whereas the remainder were detected in single environments. The resistance on 1B, detected in five environments, was attributed to Lr46 and on 7D, detected in seven environments to Lr34. The first 2B QTL corresponded with the adult plant gene, Lr13, while the second QTL corresponded with Lr16. The seedling analysis showed that Carberry carries Lr2a, Lr16, and Lr23. Five epistatic effects were identified in the population, with synergistic interactions being observed for Lr34 with Lr46, Lr16, and Lr2a. The durable rust resistance of Carberry is attributed to Lr34 and Lr46 in combination with these other resistance genes, because the resistance has remained effective even though the P. triticina population has evolved virulent to Lr2a, Lr13, Lr16, and Lr23.
Highlights
Wheat (Triticum aestivum L.) is the most widely cultivated crop globally, and it is a major source of calories and protein for the world population (Shiferaw et al, 2013; Shewry and Hey, 2015)
The variation from moderate to high correlation values observed in the leaf rust severity was consistent with the plotted distributions of the CT population across environments and suggested a partial differential response to the environment
These results were suggestive of a leaf rust resistance complex of genes in Carberry, which is supported by low to moderate heritability values
Summary
Wheat (Triticum aestivum L.) is the most widely cultivated crop globally, and it is a major source of calories and protein for the world population (Shiferaw et al, 2013; Shewry and Hey, 2015). Leaf rust was a production problem in the 1980s when the cultivar AC Barrie was the dominant wheat cultivar in the western Canada (McCallum and DePauw, 2008). Over time, improved resistance to leaf rust was achieved in western Canada by developing cultivars with additional genes for resistance (McCallum and DePauw, 2008). A hard red spring wheat cultivar, Thatcher was susceptible to leaf rust, it was the first significant stem rust resistant cultivar grown in Canada extensively over a long period of time extending from 1939 to 1968 (McCallum et al, 2007; McCallum and DePauw, 2008). Most of the designated genes confer ASR against leaf rust and some QTL, reported in different genetic backgrounds, provide APR (McIntosh et al, 2014). This study was conducted to understand the genetic basis of leaf rust resistance in Carberry through a cross with the susceptible variety, Thatcher
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