Stripe rust and leaf rust resistance QTL mapping, epistatic interactions, and co-localization with stem rust resistance loci in spring wheat evaluated over three continents

Abstract

In wheat, advantageous gene-rich or pleiotropic regions for stripe, leaf, and stem rust and epistatic interactions between rust resistance loci should be accounted for in plant breeding strategies. Leaf rust (Puccinia triticina Eriks.) and stripe rust (Puccinia striiformis f. tritici Eriks) contribute to major production losses in many regions worldwide. The objectives of this research were to identify and study epistatic interactions of quantitative trait loci (QTL) for stripe and leaf rust resistance in a doubled haploid (DH) population derived from the cross of Canadian wheat cultivars, AC Cadillac and Carberry. The relationship of leaf and stripe rust resistance QTL that co-located with stem rust resistance QTL previously mapped in this population was also investigated. The Carberry/AC Cadillac population was genotyped with DArT(®) and simple sequence repeat markers. The parents and population were phenotyped for stripe rust severity and infection response in field rust nurseries in Kenya (Njoro), Canada (Swift Current), and New Zealand (Lincoln); and for leaf rust severity and infection response in field nurseries in Canada (Swift Current) and New Zealand (Lincoln). AC Cadillac was a source of stripe rust resistance QTL on chromosomes 2A, 2B, 3A, 3B, 5B, and 7B; and Carberry was a source of resistance on chromosomes 2B, 4B, and 7A. AC Cadillac contributed QTL for resistance to leaf rust on chromosome 2A and Carberry contributed QTL on chromosomes 2B and 4B. Stripe rust resistance QTL co-localized with previously reported stem rust resistance QTL on 2B, 3B, and 7B, while leaf rust resistance QTL co-localized with 4B stem rust resistance QTL. Several epistatic interactions were identified both for stripe and leaf rust resistance QTL. We have identified useful combinations of genetic loci with main and epistatic effects. Multiple disease resistance regions identified on chromosomes 2A, 2B, 3B, 4B, 5B, and 7B are prime candidates for further investigation and validation of their broad resistance.

QTL Analysis for Drought Tolerance in Wheat: Present Status and Future Possibilities

“…Epistasis has been shown to contribute substantially to the genetic variation for a number of complex traits (e.g., adaptation to drought, heat, and salinity) in crops including wheat and other cereals [62][63][64]. Therefore, the identification of epistatic QTLs is essential for the development of efficient marker-assisted selection (MAS) schemes for complex traits such as drought tolerance, aimed at improving breeding efficiency [65].…”

A QTL with major effect on reducing leaf rust severity on the short arm of chromosome 1A of wheat detected across different genetic backgrounds and diverse environments

“…Currently, 73 formally and more than 10 temporarily designated Lr genes have been described for hexaploid wheat (McIntosh et al 2013;Buerstmayr et al 2014;Li et al 2014;Park et al 2014), and more than 80 leaf rust-resistance QTLs have been mapped (e.g., Buerstmayr et al 2014;Li et al 2014;Singh et al 2014;Tsilo et al 2014;Zhou et al 2014). QLr.cau-1AS was mapped on chromosome arm 1AS with the resistant allele being contributed by Luke.…”

“…This type of resistance is often quantified in the field by lower disease severity or smaller area under the disease progress curve (AUDPC) compared with a susceptible genotype, or in the greenhouse by longer latent period, smaller pustule size, lower pustule density, etc. Li et al (2014) provided a review about QTL for leaf rust-resistance in wheat published before 2013, summarizing about 80 QTLs assigned to 16 chromosomes, and additional QTLs were reported recently (e.g., Buerstmayr et al 2014;Singh et al 2014;Tsilo et al 2014;Zhou et al 2014). Slow-rusting resistance can be genetically mapped in chromosome regions delimited by DNA markers through QTL analysis, and it can be selected on the basis of tightly linked DNA markers.…”

<b>Genetic effects for controlling stripe rust (<i>Puccinia striiformis</i> f. sp. <i>tritici</i>) resistance in wheat through joint segregation analysis

“…Past studies revealed that the AUDPC in wheat crosses was controlled by additive dominance epistatic effect of two major genes plus polygene (Khan et al, 2009a). In QTLs mapping for leaf and stripe rust in wheat, Singh et al (2014) also identified several epistatic effects both for both rusts resistance QTL. In wheat cultivars, the AUDPC was controlled by three/four genes in cv.…”

“…In our continent, leaf and stripe rust affects the production on approximately 60 (63%) and 43 (46%) million hectares, respectively, if susceptible cultivars are grown (Singh et al, 2014). Due to the mutagenic nature of rust pathogens, new resistant cultivars are rendered susceptible after sometime and usually become ineffective (Ghaledozdani, 2005).…”