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conferring resistance to stripe rust in bread and durum wheats (McIntosh et al. in
MacGenes 2010 ).
Utilization of genetic resistance and its incorporation in wheat demands genetic
resources with enormous potential. These genetic resources have been categorized
as wild relatives, elite cultivars and landraces (Bux et al . 2012a ; Kazi et al. 2012 ;
Arif et al. 2012 ). Wild progenitors of wheat possess abundant unutilized genetic
diversity. There are several stripe rust resistance genes derived from wild relatives
like Yr5 from T. spelta (Kema 1992 ), Yr8 from Ae. comosa (Riley et al. 1968 ),
Yr9 from Secale cereal e (Zeller 1973 ), Yr28 from Ae. tauschii (Singh et al. 1998 ),
Yr37 from Ae. kotschyi (Marais et al. 2005 ), Yr38 from Ae. sharonensis (Marais
et al. 2006 ), Yr40 from Ae. geniculata (Kuraparthy et al. 2007 ) and Yr42 from Ae.
neglecta (Marias et al. 2009 ). Recently, Ren et al. ( 2012 ) tagged a Yr gene in syn-
thetic hexaploid line C110 and designated the gene as YrC110. Unfortunately, no
resistance gene to stripe rust has been identified and transferred to wheat from the
A-genome diploid progenitors T. monococcum and T. urartu.
Stem Rust
Stem rust (  Puccinia graminis tritici ) resistance got high attention after the new race
TTKSK (UG99) emerged in Uganda in 1999 (Pretorius et al. 2000 ). Stem rust per
se has the potential to devastate wheat in all continents (Dubin and Brennan 2009 ;
Hodson 2011 ) The subsequent spread of TTKSK in that region soon found it to
attack wheat in Kenya, Ethiopia, Yemen reaching up to Iran throwing the SE Asia
region in jeopardy as the migration trends could take the pathogen into Pakistan
and beyond. CIMMYT wheat breeding program had been utilizing the D genome
synthetics for various other attributes and advanced derivatives screened in Kenya
gave encouraging resistant results. Selections were high yielding and also UG99
resistant (Singh et al. 2011a , b) show promise and the danger from its spread some-
what reduced. Global alliances and funding have alleviated the hazard from this
new race and also from its mutant forms. The threat of the race and its lineage has
been substantiated (Singh et al. 2008 ).
In Pakistan exists a local race of stem rust that has shown virulence and is an
added concern for that region. We have advocated that screening against this race
should be a priority and from the resistant selections further evaluations be made in
Kenya to ensure that final selections have resistance against both forms (i.e. UG99,
mutants, and the local Pakistan race).
Resistance gene Sr2 provided stability to wheat varieties with the release of Ya-
qui 50 in Mexico and other Sr2 carrying wheats released since then stabilized the
stem rust situation in Mexico and other countries where semi-dwarf wheats got
adopted. When present alone Sr2 gene confers slow rusting that is inadequate under
heavy disease pressure but does provide satisfactory resistance when it is in combi-
nation with other minor genes. Identifying/developing adapted resistant cultivars in
a relatively short time and replacing the susceptible cultivars before rust migrates
into our terrain is the strategy to mitigate potential losses. Although several genes
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