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. 1994 Jul;137(3):867–874. doi: 10.1093/genetics/137.3.867

Mutants of Downy Mildew Resistance in Lactuca Sativa (Lettuce)

P A Okubara 1, P A Anderson 1, O E Ochoa 1, R W Michelmore 1
PMCID: PMC1206046  PMID: 8088530

Abstract

As part of our investigation of disease resistance in lettuce, we generated mutants that have lost resistance to Bremia lactucae, the casual fungus of downy mildew. Using a rapid and reliable screen, we identified 16 distinct mutants of Latuca sativa that have lost activity of one of four different downy mildew resistance genes (Dm). In all mutants, only a single Dm specificity was affected. Genetic analysis indicated that the lesions segregated as single, recessive mutations at the Dm loci. Dm3 was inactivated in nine of the mutants. One of five Dm1 mutants was selected from a population of untreated seeds and therefore carried a spontaneous mutation. All other Dm1, Dm3, Dm5/8 and Dm7 mutants were derived from γ- or fast neutron-irradiated seed. In two separate Dm1 mutants and in each of the eight Dm3 mutants analyzed, at least one closely linked molecular marker was absent. Also, high molecular weight genomic DNA fragments that hybridized to a tightly linked molecular marker in wild type were either missing entirely or were truncated in two of the Dm3 mutants, providing additional evidence that deletions had occurred in these mutants. Absence of mutations at loci epistatic to the Dm genes suggested that such loci were either members of multigene families, were critical for plant survival, or encoded components of duplicated pathways for resistance; alternatively, the genes determining downy mildew resistance might be limited to the Dm loci.

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Selected References

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  1. Bonas U., Conrads-Strauch J., Balbo I. Resistance in tomato to Xanthomonas campestris pv vesicatoria is determined by alleles of the pepper-specific avirulence gene avrBs3. Mol Gen Genet. 1993 Apr;238(1-2):261–269. doi: 10.1007/BF00279555. [DOI] [PubMed] [Google Scholar]
  2. Johal G. S., Briggs S. P. Reductase activity encoded by the HM1 disease resistance gene in maize. Science. 1992 Nov 6;258(5084):985–987. doi: 10.1126/science.1359642. [DOI] [PubMed] [Google Scholar]
  3. Keen N. T. Gene-for-gene complementarity in plant-pathogen interactions. Annu Rev Genet. 1990;24:447–463. doi: 10.1146/annurev.ge.24.120190.002311. [DOI] [PubMed] [Google Scholar]
  4. Kesseli R. V., Paran I., Michelmore R. W. Analysis of a detailed genetic linkage map of Lactuca sativa (lettuce) constructed from RFLP and RAPD markers. Genetics. 1994 Apr;136(4):1435–1446. doi: 10.1093/genetics/136.4.1435. [DOI] [PMC free article] [PubMed] [Google Scholar]
  5. Knoop V., Staskawicz B., Bonas U. Expression of the avirulence gene avrBs3 from Xanthomonas campestris pv. vesicatoria is not under the control of hrp genes and is independent of plant factors. J Bacteriol. 1991 Nov;173(22):7142–7150. doi: 10.1128/jb.173.22.7142-7150.1991. [DOI] [PMC free article] [PubMed] [Google Scholar]
  6. Kunkel B. N., Bent A. F., Dahlbeck D., Innes R. W., Staskawicz B. J. RPS2, an Arabidopsis disease resistance locus specifying recognition of Pseudomonas syringae strains expressing the avirulence gene avrRpt2. Plant Cell. 1993 Aug;5(8):865–875. doi: 10.1105/tpc.5.8.865. [DOI] [PMC free article] [PubMed] [Google Scholar]
  7. Lander E. S., Green P., Abrahamson J., Barlow A., Daly M. J., Lincoln S. E., Newberg L. A., Newburg L. MAPMAKER: an interactive computer package for constructing primary genetic linkage maps of experimental and natural populations. Genomics. 1987 Oct;1(2):174–181. doi: 10.1016/0888-7543(87)90010-3. [DOI] [PubMed] [Google Scholar]
  8. Liang P., Pardee A. B. Differential display of eukaryotic messenger RNA by means of the polymerase chain reaction. Science. 1992 Aug 14;257(5072):967–971. doi: 10.1126/science.1354393. [DOI] [PubMed] [Google Scholar]
  9. Lisitsyn N., Lisitsyn N., Wigler M. Cloning the differences between two complex genomes. Science. 1993 Feb 12;259(5097):946–951. doi: 10.1126/science.8438152. [DOI] [PubMed] [Google Scholar]
  10. Martin G. B., Brommonschenkel S. H., Chunwongse J., Frary A., Ganal M. W., Spivey R., Wu T., Earle E. D., Tanksley S. D. Map-based cloning of a protein kinase gene conferring disease resistance in tomato. Science. 1993 Nov 26;262(5138):1432–1436. doi: 10.1126/science.7902614. [DOI] [PubMed] [Google Scholar]
  11. Paran I., Kesseli R. V., Westphal L., Michelmore R. W. Recent amplification of triose phosphate isomerase related sequences in lettuce. Genome. 1992 Aug;35(4):627–635. doi: 10.1139/g92-094. [DOI] [PubMed] [Google Scholar]
  12. Shirley B. W., Hanley S., Goodman H. M. Effects of ionizing radiation on a plant genome: analysis of two Arabidopsis transparent testa mutations. Plant Cell. 1992 Mar;4(3):333–347. doi: 10.1105/tpc.4.3.333. [DOI] [PMC free article] [PubMed] [Google Scholar]
  13. Straus D., Ausubel F. M. Genomic subtraction for cloning DNA corresponding to deletion mutations. Proc Natl Acad Sci U S A. 1990 Mar;87(5):1889–1893. doi: 10.1073/pnas.87.5.1889. [DOI] [PMC free article] [PubMed] [Google Scholar]
  14. Tamaki S. J., Kobayashi D. Y., Keen N. T. Sequence domains required for the activity of avirulence genes avrB and avrC from Pseudomonas syringae pv. glycinea. J Bacteriol. 1991 Jan;173(1):301–307. doi: 10.1128/jb.173.1.301-307.1991. [DOI] [PMC free article] [PubMed] [Google Scholar]
  15. Williams J. G., Kubelik A. R., Livak K. J., Rafalski J. A., Tingey S. V. DNA polymorphisms amplified by arbitrary primers are useful as genetic markers. Nucleic Acids Res. 1990 Nov 25;18(22):6531–6535. doi: 10.1093/nar/18.22.6531. [DOI] [PMC free article] [PubMed] [Google Scholar]
  16. Wing R. A., Rastogi V. K., Zhang H. B., Paterson A. H., Tanksley S. D. An improved method of plant megabase DNA isolation in agarose microbeads suitable for physical mapping and YAC cloning. Plant J. 1993 Nov;4(5):893–898. doi: 10.1046/j.1365-313x.1993.04050893.x. [DOI] [PubMed] [Google Scholar]
  17. Yu G. L., Katagiri F., Ausubel F. M. Arabidopsis mutations at the RPS2 locus result in loss of resistance to Pseudomonas syringae strains expressing the avirulence gene avrRpt2. Mol Plant Microbe Interact. 1993 Jul-Aug;6(4):434–443. doi: 10.1094/mpmi-6-434. [DOI] [PubMed] [Google Scholar]

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