Identification of Resistance to New Virulent Races of Rust in Sunflowers and Validation of DNA Markers in the Gene Pool (original) (raw)
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Marker-assisted selection for two rust resistance genes in sunflower
Molecular Breeding, 1998
In this study we report on the identification of molecular markers, OX20 600 and OO04 950 , linked to the gene R Adv in the proprietary inbred line P2. This gene confers resistance to most of the pathotypes of Puccinia helianthi identified in Australia. Analysis indicates these RAPD markers are linked to the resistance locus at 0.0 cM and 11 cM respectively. SCAR markers SCX20 600 and SCO04 950 derived from these two RAPD markers, and SCT06 950 derived from a previously reported RAPD marker linked at 4.5 cM from the R 1 rust resistance gene were developed. SCX20 600 and SCO04 950 were linked at similar distances from their resistance locus as the RAPD markers. SCTO6 950 co-segregated completely with rust resistance. The robustness of the R 1 SCAR marker was demonstrated through the amplification of the marker in a diverse range of sunflower germplasm considered to possess the R 1 gene. The SCAR markers for R Adv were not amplified in the sunflower rust differential set thereby supporting the contention that this is a novel resistance gene. They did amplify in a number of proprietary lines closely related to the line P2. This locus is under further investigation as it will be useful in our attempts to use molecular-assisted breeding to produce durable resistance in sunflower to P. helianthi.
Molecular mapping of a sunflower rust resistance gene from HAR6
Sunflower rust, caused by Puccinia helianthi Schw., can result in significant yield losses in cultivated sunflower (Helianthus annuus L. var. macrocarpus Ckll.). HAR6 is a germplasm population resistant to most predominant rust races. The objectives of this study were to map the resistance factor present in HAR6 (R HAR6 ), and to provide and validate molecular tools for the identification of this gene for marker assisted selection purposes. Virulence reaction of seedlings for the F 2 population and F 2:3 families suggested that a single dominant gene confers rust resistance in HAR6-1, a selected rust resistance line from the original population. Genetic mapping with eight markers covered 97.4 cM of genetic distance on linkage group 13 of the sunflower consensus map. A co-dominant marker ZVG61 is the closest marker distal to R HAR6 at a genetic distance of 0.7 cM, while ORS581, a dominant marker linked in the coupling phase, is proximal to R HAR6 at a genetic distance of 1.5 cM. Validation of these markers was assessed by converting a susceptible line into a rust resistant isoline by means of marker assisted backcrossing. The application of these results to assist the breeding process and to design new strategies for rust control in sunflower is discussed.
Genome, 1994
BUSH, A.L., WISE, R.P., . Restriction fragment length polymorphisms linked to genes for resistance to crown rust (Puccinia coronata) in near-isogenic lines of hexaploid oat (Avena sativa). Genome, 37: 823-83 1. Crown rust, perhaps the most important fungal disease of oat, is caused by Puccinia coronata. An examination of near-isogenic lines (NILs) of hexaploid oat (Avena sutiva) was conducted to identify markers linked to genes for resistance to crown rust. These lines were created such that a unique resistance gene is present in each of the two recurrent parent backgrounds. The six NILs of the current study, X434-11, X466-I, and Y345 (recurrent parent C237-89) and D486, D494, and D526 (recurrent parent Lang), thus provide a pair of lines to study each of three resistance genes. Restriction fragment length polymorphisms and resistance loci were mapped using BClF2 populations. Three markers were found linked to a locus for resistance to crown rust race 203, the closest at 1.9 cM in line D494 and 3.8 cM in line X466-I. In lines D526 and Y345 a marker was placed 1 . O and 1.9 cM, respectively, from the locus conferring resistance to crown rust race 345, and in D486 and X434-I1 a marker mapped at 8.0 and 10.2 cM from the locus for resistance to rust race 264B.
Theoretical and Applied Genetics, 2005
Host-plant resistance is the most economically viable and environmentally responsible method of control for Puccinia triticina, the causal agent of leaf rust in wheat (Triticum aestivum L.). The identification and utilization of new resistance sources is critical to the continued development of improved cultivars as shifts in pathogen races cause the effectiveness of widely deployed genes to be short lived. The objectives of this research were to identify and tag new leaf rust resistance genes. Forty landraces from Afghanistan and Iran were obtained from the National Plant Germplasm System and evaluated under field conditions at two locations in Texas. PI 289824, a landrace from Iran, was highly resistant under field infection. Further evaluation revealed that PI 289824 is highly resistant to a broad spectrum of leaf rust races, including the currently prevalent races of leaf rust in the Great Plains area of the USA. Eight F1 plants, 176 F2 individuals and 139 F2:3 families of a cross between PI 289824 and T112 (susceptible) were evaluated for resistance to leaf rust at the seedling stage. Genetic analysis indicated resistance in PI 289824 is controlled by a single dominant gene. The AFLP analyses resulted in the identification of a marker (P39 M48-367) linked to resistance. The diagnostic AFLP band was sequenced and that sequence information was used to develop an STS marker (TXW200) linked to the gene at a distance of 2.3 cM. The addition of microsatellite markers allowed the gene to be mapped to the short arm of Chromosome 5B. The only resistance gene to be assigned to Chr 5BS is Lr52. The Lr52 gene was reported to be 16.5 cM distal to Xgwm443 while the gene in PI 289824 mapped 16.7 cM proximal to Xgwm443. Allelism tests are needed to determine the relationship between the gene in PI 289824 and Lr52. If the reported map positions are correct, the gene in PI 289824 is unique.
Genomic Prediction of Genetic Values for Resistance to Wheat Rusts
The Plant Genome, 2012
Durable resistance to the rust diseases of wheat (Triticum aestivum L.) can be achieved by developing lines that have racenonspecifi c adult plant resistance conferred by multiple minor slow-rusting genes. Genomic selection (GS) is a promising tool for accumulating favorable alleles of slow-rusting genes. In this study, fi ve CIMMYT wheat populations evaluated for resistance were used to predict resistance to stem rust (Puccinia graminis) and yellow rust (Puccinia striiformis) using Bayesian least absolute shrinkage and selection operator (LASSO) (BL), ridge regression (RR), and s upport vector regression with linear or radial basis function kernel models. All parents and populations were genotyped using 1400 Diversity Arrays Technology markers and different prediction problems were assessed. Results show that prediction ability for yellow rust was lower than for stem rust, probably due to differences in the conditions of infection of both diseases. For within population and environment, the correlation between predicted and observed values (Pearson's correlation [ρ]) was greater than 0.50 in 90% of the evaluations whereas for yellow rust, ρ ranged from 0.0637 to 0.6253. The BL and RR models have similar prediction ability, with a slight superiority of the BL confi rming reports about the additive nature of rust resistance. When making predictions between environments and/or between populations, including information from another environment or environments or another population or populations improved prediction. R UST DISEASES are an important cause of wheat production losses worldwide. Puccinia graminis (stem rust) and Puccinia striiformis (yellow rust) continue to cause major economic losses in various parts of the world and hence receive attention in wheat breeding programs. New races of these fungi have caused yield losses even in areas where the rusts have rarely been detected, and they are more threatening to wheat worldwide than older races (Singh et al., 2011). Regions with vulnerability to yellow rust include, among others, the United States, Asia, and Oceania (Wellings, 2011). Stem rust has also become epidemic in Africa (Singh et al., 2011). Inheritance of rust resistance in wheat can be either qualitative or quantitative. Quantitative disease resistance is more durable but more diffi cult to evaluate because it is expressed in mature plants (adult plant resistance) (Rutkoski et al., 2011). Phenotyping adult plant resistance in large populations is expensive and labor intensive. Expertise is needed because expression is aff ected by, among other factors, the inoculum load and sequential infection (Hickey et al., 2012). Regarding fi nancial costs, in CIMMYT the most basic fi eld assay costs around US$30 to 40 per genotype (with two replications per location); however, if greenhouse screening is required, the cost increases signifi cantly. In
Heredity, 2005
Crown rust resistance is an important selection criterion in ryegrass breeding. The disease, caused by the biotrophic fungus Puccinia coronata, causes yield losses and reduced quality. In this study, we used linkage mapping and QTL analysis to unravel the genomic organization of crown rust resistance in a Lolium perenne population. The progeny of a pair cross between a susceptible and a resistant plant were analysed for crown rust resistance. A linkage map, consisting of 227 loci (AFLP, SSR, RFLP and STS) and spanning 744 cM, was generated using the two-way pseudo-testcross approach from 252 individuals. QTL analysis revealed four genomic regions involved in crown rust resistance. Two QTLs were located on LG1 (LpPc4 and LpPc2) and two on LG2 (LpPc3 and LpPc1). They explain 12.5, 24.9, 5.5 and 2.6% of phenotypic variance, respectively. An STS marker, showing homology to R genes, maps in the proximity of LpPc2. Further research is, however, necessary to check the presence of functional R genes in this region. Synteny at the QTL level between homologous groups of chromosomes within the Gramineae was observed. LG1 and LG2 show homology with group A and B chromosomes of oat on which crown rust-resistance genes have been identified, and with the group 1 chromosomes of the Triticeae, on which leaf rustresistance genes have been mapped. These results are of major importance for understanding the molecular background of crown rust resistance in ryegrasses. The identified markers linked to crown rust resistance have the potential for use in marker-assisted breeding. Heredity (2005) 95, 348-357.
Theoretical and Applied Genetics, 2009
Over time, many single, all-stage resistance genes to stripe rust (Puccinia striiformis f. sp. tritici) in wheat (Triticum aestivum L.) are circumvented by race changes in the pathogen. In contrast, high-temperature, adult-plant resistance (HTAP), which only is expressed during the adult-plant stage and when air temperatures are warm, provides durable protection against stripe rust. Our objective was to identify major quantitative trait loci (QTL) for HTAP resistance to stripe rust in the spring wheat cultivar 'Louise'. The mapping population consisted of 188 recombinant inbred lines (RIL) from a Louise (resistant) by 'Penawawa' (susceptible) cross. F 5:6 lines were evaluated for stripe rust reaction under natural infection in replicated field trials at five locations in the US Pacific Northwest in 2007 and 2008. Infection type (IT) and disease severity were recorded for each RIL 2-4 times per location. In all environments, Penawawa, the susceptible parent, was rated with an IT ranging from 6 to 8 at all growth stages evaluated. In contrast, Louise, the resistant parent, was rated with an IT of 2 or 3 across growth stages. Distribution of IT values was bimodal, indicating a single major gene was affecting the trait. The parents and RIL population were evaluated with 295 polymorphic simple sequence repeat and one single nucleotide polymorphism markers. One major QTL, designated QYrlo.wpg-2BS, associated with HTAP resistance in Louise, was detected on chromosome 2BS (LOD scores ranging from 5.5 to 62.3 across locations and years) within a 16.9 cM region flanked by Xwmc474 and Xgwm148. SSR markers associated with QYrlo.wpg-2BS are currently being used in marker-based forward breeding strategies to transfer the target region into adapted germplasm to improve the durability of resistance in resulting cultivars.
Egyptian Journal of Phytopathology (Print), 2022
Detection and introgression of slow leaf rust resistance gene, Lr46 in seven parental wheat cultivars, i.e., Gemmeiza-9, Gemmeiza-11, Gemmeiza-12, Misr-1, Misr-2, Sakha-94 and Giza-171 and their F1 and F2 crosses was carried out at Bahteem Agricultural Research Station, Qaliobia governorate, Egypt. These tested cultivars varied in their reactions to leaf rust disease. The cultivars Misr-1, Misr-2, Sakha-94, and Giza-171 showed slow rust reaction meanwhile, Gemmeiza-9, Gemmeiza-11 and Gemmeiza-12 cultivars were fast rusting. Values of area under disease progress curve (AUDPC) run in a parallel line with its disease severity. Lr46 gene was found in cultivars Misr-1, Misr-2, Sakha-94, and Giza-171 and absent in cultivars Gemmeiza-9, Gemmeiza-11, Gemmeiza-12 cultivars at 300 pb. Qualitative analysis of the obtained data showed that there were no segregations in the crosses Lr46×Misr-1, Lr46×Misr-2, Lr46×Sakha94 and Lr46×Giza-171 in the F2 plants, indicating the presence of the Lr46 in these cultivars. While, segregation was found in the crosses Lr46×Gemmeiza-9, Lr46×Gemmeiza-11, Lr46×Gemmeiza-12, indicating that these cultivars do not carry Lr46 gene. Additionally, the heritability was above 94%, suggesting that the selection of genotypes resistant to leaf rust in the first generations (F2) was feasible. However, this selection is more successful in later generations because the dominance effect is critical for the expression of this trait. Molecular detection proved that Lr46 gene was inserted into Gemmeiza-9, Gemmeiza-11 and Gemmeiza-12 to have slow rust resistance in F2 plants. This saves effort and time as it is possible to rely on molecular marker assisted selection in the early selection of plants carrying this gene. Mean of the yield components, plant height, number of spikes/plant, number of kernels/plant, 100-kernel weight, and grain yield/plant of the three F2 crosses was higher than those of their parents. So, plant breeders should not rely on complete rust resistance, but should consider partial resistance, particularly slow rusting resistance genes.