Leaf Rust Resistance Genes Lr9 Research Articles

Evaluation of the resistance to Chinese predominant races of Puccinia triticina and analysis of effective leaf rust resistance genes in wheat accessions from the U.S. National Plant Germplasm System.

Puccinia triticina, which is the causative agent of wheat leaf rust, is widely spread in China and most other wheat-planting countries around the globe. Cultivating resistant wheat cultivars is the most economical, effective, and environmentally friendly method for controlling leaf rust-caused yield damage. Exploring the source of resistance is very important in wheat resistance breeding programs. In order to explore more effective resistance sources for wheat leaf rust, the resistance of 112 wheat accessions introduced from the U.S. National Plant Germplasm System were identified using a mixture of pathogenic isolates of THTT, THTS, PHTT, THJT and THJS which are the most predominant races in China. As a result, all of these accessions showed high resistance at seedling stage, of which, ninety-nine accessions exhibited resistance at adult plant stage. Eleven molecular markers of eight effective leaf rust resistance genes in China were used to screen the 112 accessions. Seven effective leaf rust resistance genes Lr9, Lr19, Lr24, Lr28, Lr29, Lr38 and Lr45 were detected, except Lr47. Twenty-three accessions had only one of those seven effective leaf rust resistance gene. Eleven accessions carried Lr24+Lr38, and 7 accessions carried Lr9+Lr24+Lr38, Lr24+Lr38+Lr45, Lr24+Lr29+Lr38 and Lr19+Lr38+Lr45 respectively. The remaining seventy-one accessions had none of those eight effective leaf rust resistance genes. This study will provide theoretical guidance for rational utilization of these introduted wheat accessions directly or for breeding the resistant wheat cultivars.

The use of molecular-genetic and phytopathological methods to identify genes for effective leaf rust resistance in Aegilops accessions

Background. Identification of effective genes for disease resistance in resistant plant samples is the most important step toward recommending them for breeding. There are three main methods for such identification: hybridological analysis, phytopathological test, and DNA marking. The method of PCR markers is widely used in Russia to identify resistance genes in wheat relatives, including the genus Aegi lops L. for resistance to leaf rust. From a theoretical viewpoint, the presence of a certain amplification fragment can hardly be interpreted as a definite proof of the presence of a resistance gene: during the species evolution, recombinations and mutations could occur, resulting in disturbance of the fragment’s presence and phenotypic expression of its connection with resistance. The purpose of this work was a comparison between molecular-genetic and phytopathological methods to identify leaf rust resistance genes Lr9 and Lr41 in three Aegilops species.Materials and methods. We identified leaf rust resistance genes Lr9 and Lr41 in forty Aegilops accessions using PCR with J13 and GDM35 primers, respectively. In the phytopathological test, the seedlings were infected with the pathogen population (avirulent to Lr9 and Lr41 genes) and the fungus clones virulent to the wheat line with the Lr9 gene.Results and conclusions. According to the data of molecular marking, the Lr41 gene was present in twelve Ae. tauschii Coss. accessions; Lr9 in four Ae umbellulata Zhuk. accessions and four of Ae. biuncialis Vis. All accessions of Ae. tauschii, two of Ae. umbellulata, and three of Ae. biuncialis, possessing effective resistance genes according to the molecular testing, were susceptible to the pathogen population. For three Ae. umbellulata accessions resistant to the population, where DNA marking failed to identify an Lr9 gene, the presence of this gene was shown by a phytopathological test. Thus, there were significant differences in the postulation of effective Lr9 and Lr41 leaf rust resistance genes in Aegilops accessions after a phytopatological test and the use of DNA markers.

Use of molecular markers in wheat breeding for resistance to leaf rust at the Lukyanenko Research Institute of Agriculture

Wheat accessions were genotyped with molecular markers linked to wheat leaf rust resistance genes Lr9, Lr10, Lr19, Lr24, Lr26, Lr34, and Lr37. They included 1920 wheat plants and 46 commercial varieties bred at the Lukyanenko Institute. Basically, the analyzed varieties had the inefficient gene Lr10, poorly efficient Lr26 and Lr34, or their combinations. The highly efficient genes Lr9 and Lr24 were not detected. The Lr19 gene, effective in the Krasnodar region, was identified in varieties Pallada and Yara. The resistance gene Lr37 was found in the Morozko variety. Within a short time, the F2 and F3 plants with the introgression of genes Lr9, Lr19, Lr24, and Lr37 were obtained. Accessions with combinations Lr24 +Lr37, Lr24 + Lr19, Lr24 + Lr9, Lr19 + Lr37, Lr37 + Lr9, and Lr19 + Lr9 were identified. Seven plants with the combination of three genes Lr37 + Lr19 + Lr9 and one with Lr37 + Lr24 + Lr9 were selected.

Identification of the leaf rust resistance genes Lr9, Lr26, Lr28, Lr34, and Lr35 in a collection of Iranian wheat genotypes using STS and SCAR markers

Brown rust or leaf rust is one of the most important diseases of wheat occurring almost in all wheat-producing regions and reduces crop yield. In order to produce resistant cultivars, it is necessary to identify resistance genes in different germplasms and combine them in (a) suitable stock(s). To identify the presence of the leaf rust resistance genes using STS and SCAR markers, 83 Iranian wheat genotypes, Lr near-isogenic lines in Thatcher (positive controls), and the cultivar Thatcher (negative control) were used. After growing plants in the greenhouse, DNA was extracted by SDS method. Following that, polymerse chain reaction was performed for the markers of the resistance genes Lr9, Lr26, Lr28, Lr34, and Lr35 which amplified 1,100, 1,100, 378, 150, and 900 bp bands, respectively. Based on the results, the resistance genes Lr9 and Lr35 were only present in the positive controls. The resistance gene Lr26 was only detected in four cultivars; Arta, Pishtaz, Shiroodi, and Falat, and the gene Lr34 was present in six cultivars (Akbari, Bam, Tajan, Khazar 1, Sistan and Niknezhad). The Lr28 primer amplified a band of the same size in all genotypes even the negative control and therefore the presence/absence of this gene could not be validated. These results indicate the necessity for designing a specific primer for Lr28. In general, only the genes Lr26 and Lr34 were present in some genotypes. The genes Lr9 and Lr35 were not present in this collection and as based on rust surveys, no virulence has been detected for Lr9 and Lr28, so they could be transferred to suitable lines from donor sources.

Identification of a leaf-rust resistance gene in species of Aegilops L., synthetic forms, and introgression lines of common wheat

DNA samples of wild relatives, synthetic forms, and introgression lines of common wheat (Triticum aestivum L.) were genotyped with diagnostic molecular markers that are linked to the leaf-rust resistance genes Lr9, Lr35, and Lr47. The Lr9 gene was identified in Aegilops umbellulata and Lr35 and Lr47 were identified in Ae. speltoides. The synthetic forms Avrolata and Avrodes, in which the genomes of Ae. umbellulata and Ae. speltoides, respectively, replaced the wheat D genome, contain the Lr9 and Lr35 genes. The genomes of the introgression lines that were developed using Ae. umbellulata lack Lr9. The Lr35 gene is present in one of the introgression lines that was derived from Avrodes. Some of the wild relatives and the introgression lines may contain additional leaf-rust resistance genes.

Validity of selected DNA markers for breeding leaf rust resistant wheat

The set of 44 near-isogenic lines of spring wheat cv. Thatcher and wheat genotypes known to carry specific leaf rust resistance genes were included in the present study for the preliminary validation of twelve STS and SCAR markers linked to leaf rust resistance genes Lr9, Lr19, Lr20, Lr21, Lr24, Lr25, Lr26, Lr28, Lr29, Lr37. Seven Lr genes were specifically tagged by STS and SCAR markers. The presence of genes Lr9, Lr19, Lr20, Lr24, Lr28, Lr29, Lr37 in the tested plant materials was confirmed by a unique amplification of markers SCS5 550, SCS265 512 and SCS253 736, STS638, SCS73 719, SCS421 570, IPY10 and Lr29F24/R24, cslVrgal3, PS10R/L, respectively. Evaluation of the repeatability and the reliability of selected markers (pTAG621 for Lr1, STS683 for Lr20, D14L for Lr21, Lr25F20/R19 for Lr25, Lr29F24/R24, IPY10 for Lr29, cslVrgal3 for Lr37 and PS10R/L for Lr47) across four European laboratories and PCR conditions demonstrated the usability of STS638, Lr29F24/R24, IPY10, cslVrgal3 and PS10R/L markers in marker-assisted selection. STS markers pTAG621 for gene Lr1, D14L for gene Lr21, Lr25F20/R19 for gene Lr25 were found to be unsuitable for effective screening of large segregating populations in breeding programs.

Detection of Leaf Rust Resistance Genes Lr9 and Lr10 in Wheat (Triticum aestivum) by PCR Based STS Markers

Leaf rust resistance genes Lr9 and Lr10 were detected in wheat (Triticum aestivum) genotypes by PCR based STS markers. Out of sixty-two elite wheat genotypes, screened for the presence of leaf rust resistance gene Lr10, nineteen genotypes revealed the presence through PCR analysis with the primers specific to Lr10 gene. Validation of the marker for Lr9 gene in the parental lines followed by successful detection of the gene in F4 lines out of cross HP1633 (Lr9) X HP1776, was also done. Usefulness of molecular markers for the detection of rust resistance genes in different genotypes is discussed.