Using leaf tip necrosis as a phenotypic marker to predict the presence of durable rust resistance gene pair Lr34/Yr18 in wheat (original) (raw)
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Lr46 : A Gene Conferring Slow-Rusting Resistance to Leaf Rust in Wheat
Phytopathology, 1998
Wheat (Triticum aestivum) cultivar Pavon 76 carries slow-rusting resistance to leaf rust that has remained effective in Mexico since its release in 1976. ‘Pavon 76’ was crossed with two leaf rust-susceptible wheat cultivars, Jupateco 73S and Avocet S, and between 118 and 148 individual F2 plant-derived F3 and F5 lines were evaluated for adult-plant leaf rust resistance at two field sites in Mexico during different seasons. Evaluation of F1 plants and parents indicated that the slow-rusting resistance was partially dominant. Segregation in the F3 and F5 indicated that the resistance was based on two genes with additive effects. Monosomic analysis was carried out to determine the chromosomal locations of the resistance genes. For this purpose, two or three backcross-derived cytogenetic populations were developed by crossing ‘Pavon 76’ with a monosomic series of adult-plant leaf rust-susceptible cultivar Lal-bahadur. Evaluation of such BC2F3 and BC3F3 lines from 16 confirmed ‘Lalbahadu...
Phytopathology, 2004
A major leaf rust (Puccinia triticina) resistance quantitative trait locus (QTL) (QLrP.sfr-7DS) previously has been described on chromosome 7DS in the winter wheat (Triticum aestivum) cv. Forno. It was detected in a population of single-seed descent (SSD) lines derived from the cross Arina × Forno. QLrP.sfr-7DS conferred a durable and slow-rusting resistance phenotype, co-segregated with a QTL for leaf tip necrosis (LTN) and was mapped close to Xgwm295 at a very similar location as the adult plant leaf rust resistance gene Lr34 found in some spring wheat lines. Here, we describe the validation of this QTL by mapping it to the same chromosomal region close to Xgwm295 on chromosome 7DS in a population of SSD lines from the winter wheat × spelt (T. spelta) cross Forno × Oberkulmer. In both populations, the log of the likelihood ratio curves for leaf rust resistance and LTN peaked at identical or very similar locations, indicating that both traits are due to the same gene. We have impro...
Australasian Plant Pathology, 2016
Leaf rust is one of the most destructive diseases of wheat causing huge economic losses throughout the world. Several leaf rust resistance genes have been identified and genetically mapped, some of which have also been cloned including the adult plant resistance gene Lr34. Selection of wheat genotypes carrying Lr34 can be accomplished with the help of expression of a morphological marker leaf tip necrosis (LTN) which is linked with Lr34. However, recording of LTN under field conditions is time and labor intensive thereby slowing down the process of selection of desirable genotypes. Use of molecular markers which are tightly linked to Lr34 can be more efficient in precise identification of lines carrying this gene in a short span of time. We selected a total of seven such markers that were earlier reported to be linked with Lr34. The objective of the study was to assess the suitability of these markers in distinguishing Indian bread wheat genotypes carrying Lr34 from those which lacked Lr34. The haplotype analysis suggested that one STS marker (csLV34) and two gene specific markers (cssfr2 and cssfr5) could distinguish wheat genotypes carrying Lr34 from those lacking it. Use of these markers in breeding program can accelerate the speed of selection of desirable genotypes.
Effect of Leaf Rust Resistance Gene Lr34 on Grain Yield and Agronomic Traits of Spring Wheat
Crop Science, 1997
Leaf rust, caused by Puccinia recondita Roberge ex Desmaz. f. sp. tritici, is an important disease of wheat (Triticum aestivum L.) worldwide. The Lr34 gene is known to confer durable resistance. We evaluated the effect of Lr34 on grain yield and other traits in the absence and presence of leaf rust. 'Jupateco 73R' and 'Jupateco 73S' (near-isogenic reselection from the Mexican spring wheat cultivar 'Jupateco 73' for the presence and absence of Lr34, respectively) and 22 random inbred F 6 lines, 11 with and 11 without Lr34 (derived from the cross 'Jupateco 73R/Jupateco 73S'), were planted in replicated field trials during the 1992-1993 and 1993-1994 seasons in northwestern Mexico. The mean grain yield of Jupateco 73R was 5.9% lower (P < 0.05) than that of Jupateco 73S in protected plots in the 1992-1993 experiment. Significant reductions (P < 0.05) were also observed for biomass, kernels per spike and kernels m~2. Significant (P < 0.01) reductions of 5% in mean grain yield and 3.7% in mean kernel weight were again evident in one of the two experiments sown during the 1993-1994 season. Comparison of grain yield in protected and nonprotected treatments indicated that though leaf rust could significantly (P < 0.01) reduce grain yield by approximately 15% in the presence ofLr34, the reductions in the absence ofLr34 were substantially higher and ranged between 42.5 to 84% depending on planting date and year. Reductions in all other traits were also significantly higher in the absence of Lr34. We conclude that although the presence of Lr34, which is linked with leaf tip necrosis of adult plants, may carry a slight yield penalty in some disease free environments, its use in leaf rust prone areas could provide substantial protection to grain yield and other traits. L AP RUST is an important disease of wheat worldwide. Cultivation of resistant cultivars is the most economical and environmentally benign way to reduce losses caused by the disease. Several genes are currently known to confer resistance (Mclntosh et al., 1993). Roelfs (1988) suggested that Lrl2 or Lrl3 in combination with
Characterization of Adult-Plant Resistance to Leaf Rust of Wheat Conferred by the Gene Lr22a
Plant Disease, 1987
ReseaRch W heat (Triticum aestivum L.) is a major staple food worldwide, with harvested area of >220 million ha from 2014 to 2016 (USDA-ERS, 2017). During the last decade in Mexico, wheat has been grown on 713,000 ha annually with a yield of 5.2 t ha −1 (Calvo-Salazar et al., 2015). Leaf rust and stripe rust, caused by Puccinia triticina Erikss. (Pt) and P. striiformis Westend. f. sp. tritici (Pst), respectively, are two major diseases that threaten wheat production worldwide. For example, yield losses caused by both rusts were up to 60% on susceptible cultivars (Herrera-Foessel et al., 2006; Vergara-Díaz et al., 2015). Breeding and cultivation
The Plant Genome, 2015
The partial rust resistance genes Lr34 and Sr2 have been used extensively in wheat (Triticum aestivum L.) improvement, as they confer exceptional durability. Interestingly, the resistance of Lr34 is associated with the expression of leaf tip necrosis (LTN) and Sr2 with pseudo-black chaff (PBC). Genome-wide association mapping using CIMMYT's stem rust resistance screening nursery (SRRSN) wheat lines was done to identify genotyping-bysequencing (GBS) markers linked to LTN and PBC. Phenotyping for these traits was done in Ithaca, New York (fall 2011); Njoro, Kenya (main and off-seasons, 2012), and Wellington, India (winter, 2013). Using the mixed linear model (MLM), 18 GBS markers were significantly associated with LTN. While some markers were linked to loci where the durable leaf rust resistance genes Lr34 (7DS), Lr46 (1BL), and Lr68 (7BL) were mapped, significant associations were also detected with other loci on 2BL, 5B, 3BS, 4BS, and 7BS. Twelve GBS markers linked to the Sr2 locus (3BS) and loci on 2DS, 4AL, and 7DS were significantly associated with PBC. This study provides insight into the complex genetic control of LTN and PBC. Further efforts to validate and study these loci might aid in determining the nature of their association with durable resistance.
Theoretical and Applied Genetics, 2011
The common wheat genotype 'RL6077' was believed to carry the gene Lr34/Yr18 that confers slowrusting adult plant resistance (APR) to leaf rust and stripe rust but located to a different chromosome through interchromosomal reciprocal translocation. However, haplotyping using the cloned Lr34/Yr18 diagnostic marker and the complete sequencing of the gene indicated Lr34/Yr18 is absent in RL6077. We crossed RL6077 with the susceptible parent 'Avocet' and developed F 3 , F 4 and F 6 populations from photoperiod-insensitive F 3 lines that were segregating for resistance to leaf rust and stripe rust. The populations were characterized for leaf rust resistance at two Mexican sites, Cd. Obregon during the
Phenotypic association of adult-plant resistance to leaf and stripe rusts in wheat
Canadian Journal of Plant Pathology, 2005
Association of resistance to multiple diseases is of interest to plant breeders as it simplifies the breeding process. Phenotypic association of adult-plant resistance to leaf and stripe rusts, caused by Puccinia triticina and Puccinia striiformis f. sp. tritici, respectively, was studied in F 5 wheat lines derived from a diallel cross involving one susceptible and five resistant genotypes. Resistance in the parental genotypes was formerly identified as being conditioned by the Lr34/Yr18 linkage on chromosome arm 7DS, in addition to at least two to three genes with additive effects. Adult-plant resistance to leaf rust was found to be closely associated with resistance to stripe rust in the wheat genotypes examined in this study. Results indicated that genes other than Lr34/Yr18 were also either linked or pleiotropic for resistance to both diseases. This linkage or pleiotropic effect, however, did not seem to occur in every instance. Resistance genes other than Lr34/Yr18 were estimated to have contributed to 40% and 43% reductions in severity of leaf and stripe rusts, respectively, while lines with a phenotype of leaf-tip necrosishad, on average, 30.5% and 20.8% less severity for leaf and stripe rusts, respectively.
Genetic analysis of durable leaf rust resistance in winter wheat
TAG Theoretical and Applied Genetics, 2000
Quantitative resistance that delays the epidemic development of leaf rust in wheat is an important source for durable resistance breeding. The Swiss winter wheat variety 'Forno' shows a high level of quantitative resistance against leaf rust. This resistance has been effective for more than 10 years and can therefore be considered to be durable. In order to map quantitative trait loci (QTL) for durable leaf rust resistance we analysed 204 F 5 recombinant inbred lines (RILs) of the cross between the winter wheat 'Forno' and the winter spelt 'Oberkulmer' for their level of leaf rust resistance (LR) and leaf tip necrosis (LTN) in four different environments. Both traits showed a continuous distribution and were significantly correlated (r=−0.5). Across environments we detected 8 QTL for leaf rust resistance (6 inherited from 'Forno') and 10 QTL for the quantitative expression of LTN (6 inherited from 'Forno'). Of the 6 QTL responsible for the durable leaf rust resistance of 'Forno', 1 major QTL coincided with a thaumatin locus on 7BL explaining 35% of the phenotypic variance. Four QTL for LR coincided with QTL for LTN. At these loci the alleles of 'Forno' increased the level of resistance as well as the extent of LTN, indicating pleiotropy.