title: The Lr34 adult plant rust resistance gene provides seedling resistance in durum wheat without senescence.
abstract: The hexaploid wheat (Triticum aestivum) adult plant resistance gene, Lr34/Yr18/Sr57/Pm38/Ltn1, provides broad-spectrum resistance to wheat leaf rust (Lr34), stripe rust (Yr18), stem rust (Sr57) and powdery mildew (Pm38) pathogens, and has remained effective in wheat crops for many decades. The partial resistance provided by this gene is only apparent in adult plants and not effective in field-grown seedlings. Lr34 also causes leaf tip necrosis (Ltn1) in mature adult plant leaves when grown under field conditions. This D genome-encoded bread wheat gene was transferred to tetraploid durum wheat (T. turgidum) cultivar Stewart by transformation. Transgenic durum lines were produced with elevated gene expression levels when compared with the endogenous hexaploid gene. Unlike nontransgenic hexaploid and durum control lines, these transgenic plants showed robust seedling resistance to pathogens causing wheat leaf rust, stripe rust and powdery mildew disease. The effectiveness of seedling resistance against each pathogen correlated with the level of transgene expression. No evidence of accelerated leaf necrosis or up-regulation of senescence gene markers was apparent in these seedlings, suggesting senescence is not required for Lr34 resistance, although leaf tip necrosis occurred in mature plant flag leaves. Several abiotic stress-response genes were up-regulated in these seedlings in the absence of rust infection as previously observed in adult plant flag leaves of hexaploid wheat. Increasing day length significantly increased Lr34 seedling resistance. These data demonstrate that expression of a highly durable, broad-spectrum adult plant resistance gene can be modified to provide seedling resistance in durum wheat.
authors.affiliation: CSIRO Agriculture, Canberra, ACT, Australia.
authors.forename: Amy
authors.initials: A
authors.lastname: Rinaldo
authors.affiliation: CSIRO Agriculture, Canberra, ACT, Australia.
authors.forename: Brian
authors.initials: B
authors.lastname: Gilbert
authors.affiliation: Department of Plant and Microbial Biology, University of Zurich, Zurich, Switzerland.
authors.forename: Rainer
authors.initials: R
authors.lastname: Boni
authors.affiliation: Department of Plant and Microbial Biology, University of Zurich, Zurich, Switzerland.
authors.forename: Simon G
authors.initials: SG
authors.lastname: Krattinger
authors.affiliation: Plant Breeding Institute, University of Sydney, Narellan, NSW, Australia.
authors.forename: Davinder
authors.initials: D
authors.lastname: Singh
authors.affiliation: Plant Breeding Institute, University of Sydney, Narellan, NSW, Australia.
authors.forename: Robert F
authors.initials: RF
authors.lastname: Park
authors.affiliation: CSIRO Agriculture, Canberra, ACT, Australia.
authors.forename: Evans
authors.initials: E
authors.lastname: Lagudah
authors.affiliation: CSIRO Agriculture, Canberra, ACT, Australia.
authors.forename: Michael
authors.initials: M
authors.lastname: Ayliffe
mesh_terms: D001487:Basidiomycota / Q000472:pathogenicity*; D060467:Disease Resistance / Q000235:genetics; D010935:Plant Diseases / Q000235:genetics; D018515:Plant Leaves / Q000235:genetics / Q000378:metabolism / Q000382:microbiology; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D030821:Plants, Genetically Modified / Q000235:genetics / Q000378:metabolism* / Q000382:microbiology*; D036226:Seedlings / Q000235:genetics / Q000378:metabolism* / Q000382:microbiology*; D014908:Triticum / Q000235:genetics / Q000378:metabolism* / Q000382:microbiology*
chemical_list: D010940:Plant Proteins
keywords: 
  Blumeria
  ; 
  Puccinia
  ; 
  Triticum
  ; ABC transporter; rust