The Lr34 adult plant rust resistance gene provides seedling resistance in durum wheat without senescence
Rinaldo A, Gilbert B, Boni R, Krattinger SG, Singh D, Park RF, Lagudah E and Ayliffe M (2017) The Lr34 adult plant rust resistance gene provides seedling resistance in durum wheat without senescence. Plant Biotechnology Journal 15: 894-905.
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.