Molecular and phenotypic characterization of seedling and adult plant leaf rust resistance in a world wheat collection

Abstract

Genetic resistance is the most effective approach to managing wheat leaf rust. The aim of this study was to characterize seedling and adult plant leaf rust resistance of a world wheat collection. Using controlled inoculation with ten races of Puccinia triticina, 14 seedling resistance genes were determined or postulated to be present in the collection. Lr1, Lr3, Lr10 and Lr20 were the most prevalent genes around the world while Lr9, Lr14b, Lr3ka and/or Lr30 and Lr26 were rare. To confirm some gene postulations, the collection was screened with gene-specific molecular markers for Lr1, Lr10, Lr21 and Lr34. Although possessing the Lr1 and/or Lr10 gene-specific marker, 51 accessions showed unexpected high infection types to P. triticina race BBBD. The collection was tested in the field, where rust resistance ranged from nearly immune or highly resistant with severity of 1 % and resistant host response to highly susceptible with severity of 84 % and susceptible host response. The majority of the accessions possessing the adult plant resistance (APR) gene Lr34 had a maximum rust severity of 0–35 %, similar to or better than accession RL6058, a Thatcher-Lr34 near-isogenic line. Many accessions displayed an immune response or a high level of resistance under field conditions, likely as a result of synergy between APR genes or between APR and seedling resistance genes. However, accessions with three or more seedling resistance genes had an overall lower field severity than those with two or fewer. Immune or highly resistant accessions are potential sources for improvement of leaf rust resistance. In addition, some lines were postulated to have known but unidentified genes/alleles or novel genes, also constituting potentially important sources of novel resistance.Electronic supplementary materialThe online version of this article (doi:10.1007/s11032-013-9899-8) contains supplementary material, which is available to authorized users.

Application of Phenotypic and Molecular Markers to Combine Genes for Durable Resistance against Rust Virulences and High Yield Potential in Wheat

“…It involved screening of wheat germplasm against leaf and yellow rust under natural and high stress inoculation conditions for selecting the lines that may show minor gene based resistance followed by transfer of this resistance to the susceptible but high yielding varieties through conventional hybridization utilizing genotypic markers as used elsewhere for the identification of genes for pyramiding rust resistance genes in bread wheat genotypes and commercial cultivars (Khan, 1987;Dakouri et al, 2013). Newly available DNA markers X-barc 352, XWMC-44, Xgwm-533 for and Lr34/Yr18, Lr46/Yr29 and Sr2/Yr30 respectively were used to assist the selection of wheat germplasm with desirable genes Suenaga et al, 2003;William et al, 2003).…”

“…some of the genotypes showed the presence of Lr34 in the molecular analysis but in the field they remained susceptible to leaf rust. This contrast in the experimental and field results may be due to random mutations, suppression or deletion or evolution of new pathotype could also be the possible reason of inability of the wheat lines to cope with the avirulences (Awan et al, 2007;Dakouri et al, 2013). Some of the genotypes did not reveal the presence of Lr34 locus when screened through molecular marker although in the field those lines exhibited moderate resistance to leaf rust.…”

“…Hence, as per our findings, lines showing low frequency of disease severity with lower AUDPC values could be considered as slow rusting lines carrying durable rust resistance against Lr34, Lr46 and Sr2 virulences, which can be utilized in breeding programs. For its relative ease, specificity and efficiency, many authors have employed PCR-based DNA markers to verify presence of leaf rust resistance in wheat (Cherukuri et al, 2003;Prabhu et al, 2004;Obert et al, 2005;Lagudah et al, 2006;Dakouri et al, 2013;Mustafa et al, 2013). Also it requires no laborious means or to wait for particular plant stage to observe time bound gene expression controlling trait of interest i.e.…”

Genetic analysis of rust resistance genes in global wheat cultivars: an overview

“…The Lr1 and Lr2 are the most common leaf rust resistance genes in American soft red winter wheat [33,41]. The Lr20 gene dominates in African germplasms, followed by South American and Asian germplasms [176]. It is also very frequent in Ethiopian wheat germplasm [177] but is found at a very low frequency in North American and British wheat germplasms [178].…”

“…It is also very frequent in Ethiopian wheat germplasm [177] but is found at a very low frequency in North American and British wheat germplasms [178]. The Lr1, Lr10 and Lr20 genes are the most frequent in Europe, while Lr1, Lr3, Lr10 and Lr20 are found at higher frequencies in Oceania [176]. The Lr20 gene is very rare in Australian germplasm, American soft red winter wheat, and Argentinian germplasm [41,122].…”