Download Yr7 - NVT Online

Genetic and Cytogenetic Studies on
Rust Resistance Genes
Peng Zhang, Robert McIntosh,
Alexander Loladze, Robert Park,
Merrill Fordyce
Characterisation of wheat lines carrying rust
resistance genes from Thinopyrum intermedium
2
Disomic addition lines Z4 and Z5
• Z4 and Z5 are disomic addition lines (2n = 44) produced from
Zhong 4 (a partial amphiploid of wheat and Th. intermedium)
• Z4 carries resistance to all three rusts and Z5 carries resistance to
stem and leaf rust
3
Translocations in Z4 and Z5
Z5
Z4
Common translocation in Z4 and Z5: 2DS.3DL-3StL (SR and LR)
Translocation only in Z4: 7AS-7StS.7StL (YR is on 7L of intermedium
chromatin)
The alien resistance genes in Z4 are not located on a single entire
intermedium chromosome but are present on two different wheat-Th.
intermedium translocation chromosomes
Study why the LR and YR genes in Z4 showing linkage despite the fact
that they are on two different translocation chromosomes
5
Preliminary data showed the LR and YR on Z4 were in pseudo-linkage,
rather than in real linkage
Hypothesis:
Pentavalent formed at Metaphase I of meiosis with wheat-intermedium
translocations at the terminal ends and a wheat-wheat translocation
(T7AL.2DL) linking them in the middle
Alternate disjunction of the pentavalent caused the wheat-alien
translocation chromosomes move to the same pole at Anaphase I
LR and YR showed pseudo-linkage despite not being present on the same
chromosome
Test of hypothesis: GISH the meiotic cells showing two translocations
at the ends of the pentavalent (in progress)
6
Development and validation of stripe rust
resistance gene combinations
7
Yr gene combination lines
•
Stripe rust NILs in Avocet S were developed by C. Wellings
•
In order to distinguish components of pathotype mixtures in the
field, combinations of two or more Yr genes were developed by
crossing single gene NILs
•
Multipathotype testing and molecular and morphological markers
were used to characterise and confirm these gene combinations
•
Molecular markers used: Yr5, Yr7, YrSp, Yr9, Yr10, Yr17, Yr18,
Yr15, Yr24, Yr26 and Yr32
8
Yr gene combination lines
Yr1/Yr6
Yr1/Yr9
Yr1/Yr10
Yr1/Yr17
Yr1/Yr26
Yr1/Yr27
Yr1/Yr32
Yr1/YrSp
Yr5/Yr26
Yr5/Yr27
Yr6/Yr27
Yr6/Yr9
Yr6/Yr17
Yr6/Yr24
Yr6/Yr32
Yr6/YrSp
Yr7/Yr17
Yr7/Yr24
Yr7/Yr27
Yr7/Yr32
Yr10/Yr15
Yr10/Yr24
Yr10/Yr26
Yr10/Yr27
Yr15/Yr26
Yr15/Yr24//Yr10
Yr17/Yr27
Yr17/Yr32
9
Yr gene combination lines
• 36 stripe rust gene combinations were produced
• Crosses of 20 new gene combinations were made in 2011
• Lines homozygous for both genes will be selected using rust
testing and/or molecular markers
10
Linkage study on the genes located on
chromosome 2B (Yr5, Yr7, YrSp and YrJubII)
11
• Yr5 and Yr7 are allelic (Zhang et al., 2009, Theor Appl Genet)
• Yr Spaldings Prolific (YrSp) is allelic to both Yr5 and Yr7
• Yr Jubilejna II (YrJubII) is linked in repulsion but not allelic to the
other 3 genes
• New evidence showed that Av+YrSp has at least two Yr genes, one is
at Yr5/Yr7 locus and the other one at YrJubII locus
12
Acknowledgement