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RFLP mapping of resistance to chlorosis induction by Pyrenophora tritici-repentis in wheat (1997)

Faris, J. D. ; Anderson, J. A. ; Francl, L. J. ; [et al.]

Springer

Theoretical and applied genetics 94 (1997), S. 98-103

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ISSN: 1432-2242

Keywords: Key wordsTriticum aestivum ; Pyrenophora tritici-repentis ; Quantitative trait loci ; Molecular mapping ; Disease resistance

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract Tan spot, caused by Pyrenophora tritici-repentis, is an economically important disease in major wheat production areas. The fungus can produce two genetically distinct symptoms on leaves of susceptible wheat genotypes: tan necrosis (nec) and extensive chlorosis (chl). Our objectives were to determine the number of genes conditioning resistance to tan spot in a population of wheat recombinant inbred lines, and map the chromosomal location of the resistance genes using RFLPs. Conidia produced by the P. tritici-repentis isolate Pti2 (nec+chl+) were used to inoculate seedlings of 135 recombinant inbred lines derived from the cross of the synthetic hexaploid wheat W-7984 with Opata 85. A subset of the population was inoculated with conidia produced by the isolates D308 (nec−chl+) and 86-124 (nec+chl−). Inoculated seedlings were rated on a scale of 1 to 5 based on lesion type. Necrosis-inducing culture filtrate produced by the isolate 86-124 was also used to screen the entire population. A map consisting of 532 markers was employed to identify significant associations between marker loci and tan spot resistance. The entire population was insensitive to culture filtrate produced by the isolate 86-124, and the entire subset was resistant to conidial inoculation of the same isolate. The population segregated for reaction to isolates D308 and Pti2, indicating that this population segregates for resistance to extensive chlorosis only, and not to tan necrosis. RFLP analysis indicated the presence of a gene with a major effect in 1AS, a gene with a minor effect in 4AL, and an interaction between the 1AS gene and a gene in 2DL. Together, these loci explained 49.0% of the variation in this population for resistance to tan spot produced by the isolate Pti2. Two regions one in 1BL and one in 3BL, were significantly associated with resistance to extensive chlorosis, but were not significant in the multiple regression model. It should be feasible to introgress these resistance loci into adapted genetic backgrounds by using a marker-assisted selection scheme.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/s001220050387

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Candidate gene analysis of quantitative disease resistance in wheat (1999)

Faris, J. D. ; Li, W. L. ; Liu, D. J. ; [et al.]

Springer

Theoretical and applied genetics 98 (1999), S. 219-225

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ISSN: 1432-2242

Keywords: Key words Wheat ; Quantitative trait loci ; Candidate gene ; Disease resistance ; Molecular mapping

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract Knowledge of the biological significance underlying quantitative trait loci (QTLs) for disease resistance is generally limited. In recent years, advances in plant-microbe interactions and genome mapping have lead to an increased understanding of the genes involved in plant defense and quantitative disease resistance. Here, we report on the application of the candidate-gene approach to the mapping of QTLs for disease resistance in a population of wheat recombinant inbreds. Over 50 loci, representing several classes of defense response (DR) genes, were placed on an existing linkage map and the genome was surveyed for QTLs associated with resistance to several diseases including tan spot, leaf rust, Karnal bunt, and stem rust. Analysis revealed QTLs with large effects in regions of putative resistance (R) genes, as previously reported. Several candidate genes, including oxalate oxidase, peroxidase, superoxide dismutase, chitinase and thaumatin, mapped within previously identified resistance QTLs and explained a greater amount of the phenotypic variation. A cluster of closely linked DR genes on the long arm of chromosome 7B, which included genes for catalase, chitinase, thaumatins and an ion channel regulator, had major effects for resistance to leaf rust of adult plants under conditions of natural infestation. The results of this study indicate that many minor resistance QTLs may be from the action of DR genes, and that the candidate-gene approach can be an efficient method of QTL identification.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/s001220051061

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Genomic mapping of defense response genes in wheat (1999)

Li, W. L. ; Faris, J. D. ; Chittoor, J. M. ; [et al.]

Springer

Theoretical and applied genetics 98 (1999), S. 226-233

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ISSN: 1432-2242

Keywords: Key words Molecular mapping ; Wheat ; Resistance ; Defense response genes

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract Defense response (DR) genes are a broad class involved in plant defense. In this study we mapped 36 probes representing seven classes of defense response genes. This collection of probes represents genes involved in the hypersensitive response (HR), pathogenesis-related (PR) genes, genes for the flavonoid metabolic pathway, genes encoding proline/glycine-rich proteins, ion channel regulators, lipoxygenase, lectin, and others. Using nullisomic-tetrasomic lines of ‘Chinese Spring’, we were able to assign at least 167 loci to the 21 chromosomes of wheat. Homoeologous group 7 chromosomes possessed the most DR loci followed by group 2. Sixty-two loci were placed on existing genetic linkage maps of wheat. Map locations indicated that the DR gene loci are not randomly distributed throughout the wheat genome, but rather are located in clusters and/or in distal gene-rich regions of the chromosomes. Knowledge of the chromosomal locations and genome organization of DR genes will be useful for candidate gene analysis of quantitative trait loci.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/s001220051062

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