Download P21 SYNERGISTIC EFFECTS OF GENE COMBINATIONS WITH

Synergistic Effects of Gene
Combinations with Lr67 and Lr34
Brent McCallum1 and Colin Hiebert1
1Morden
Research and Development Centre, Agriculture and Agri-Food Canada,
101 Route 100, Unit 100, Morden, MB, R6M 1Y5, Canada.
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Introduction
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The rust resistance gene Lr34 has provided durable resistance to
leaf rust in Canadian wheat cultivars since its introduction in the
1960s. It also provides resistance to stripe rust, stem rust and
other biotrophic diseases such as powdery mildew and barley yellow
dwarf virus (BYDV). Similarly Lr67 was discovered recently (Hiebert
et al. 2010) and also confers resistance to leaf, stem and stripe rust.
Both genes have been cloned and code for different types of cellular
transporters. One important characteristic of Lr34 is its ability to
combine in an additive or synergistic manner with other leaf rust
resistance genes, resulting in much better resistance than would be
expected given the resistance levels of lines with only one resistance
gene. This is important in Canadian wheat cultivars since many
contain Lr34 in combination with one or more additional resistance
genes. Our objective was to determine if Lr67 has a similar ability to
combine additively with other resistance genes like Lr34.
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A
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Lr34 + Lr13
Lr13
Lr34
Neither
Lr67 + Lr13
Lr13
Lr67
Neither
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B
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Materials and Methods
Results and Discussion
The four year (2012-2015) averages are shown for the lines in each
of the six populations in Figure 1. Both Lr34 and Lr67 alone were
able to reduce the level of leaf rust severity, with Lr34 being more
effective. All lines with Lr34 in combination with any of the other
resistance genes were more resistant than lines with only Lr34. The
same effect was observed for Lr67 in combination with Lr16 or Lr32.
The combination of Lr67 with Lr13 however was similar to the
resistance of Lr67 alone. The effect of the gene interactions was
the strongest for Lr32, which was also more effective than either
Lr13 or Lr16 when it was present alone.
This study demonstrates that Lr67 is similar to Lr34 in its ability to
interact synergistically or additively with other genes. Ineffective
genes such as Lr13, or to some extent Lr16 can also be useful in
combination with Lr34 or Lr67.
Leaf Rust Severity (%)
Doubled haploid populations were developed from the crosses
Lr34/Lr13, Lr67/Lr13, Lr34/Lr16, Lr67/Lr16, Lr34/Lr32, and
Lr67/Lr32, with approximately 200 progeny per population. These
populations were grown in leaf rust inoculated, irrigated, field
nurseries during four years 2012-2015, with two replications per
year. The lines were assessed for the level of leaf rust infection on
the flag leaves using a 0-100% modified Cobb scale. Molecular
markers were also run on each population to identify the
combination of resistance genes in each line.
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C
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Lr34 + Lr16
Lr16
Lr34
Neither
Lr67 + Lr16
Lr16
Lr67
Neither
Lr34 + Lr32
Lr32
Lr34
Neither
Lr67 + Lr32
Lr32
Lr67
Neither
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D
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E
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References
Hiebert, C. W., et al. 2010. An introgression on wheat chromosome
4DL in RL6077 (Thatcher*6/PI 250413) confers adult plant resistance
to stripe rust and leaf rust (Lr67). TAG 121:1083-1091.
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F
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Acknowledgements
Thanks to Elsa Reimer, Winnie McNabb, Mira Popovic and Ghassan
Mardli for technical assistance.
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Figure 1. The four year (2012-2015) average leaf rust severity on the
populations (A) Lr34/Lr13, (B) Lr67/Lr13, (C) Lr34/Lr16, (D)
Lr67/Lr16, (E) Lr34/Lr32 and (F) Lr67/Lr32.
Morden Research and Development Centre, Agriculture and Agri-Food Canada, 101 Route 100, Unit 100, Morden, MB, R6M 1Y5, Canada
Email: [email protected]