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

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

Translocations in Z4 and Z5 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

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)

Development and validation of stripe rust resistance gene combinations

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

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

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

Linkage study on the genes located on chromosome 2B (Yr5, Yr7, YrSp and YrJubII)

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

Acknowledgement