Abstract:

This investigation was focused on the assessment of genetic diversity for resistance to
stem rust and stripe rust in an international wheat nursery, genetic characterisation of
adult plant stripe rust resistance in Australian wheat cultivar Sentinel, understanding of
genetic relationship between two stem rust resistance genes (Sr 3 6 and 5r39) located on
chromosome 2B and assessment of genetic diversity for physiological traits among a set
of wheat landraces.
Ten seedling stem rust resistance genes (Sr8a, Sr8b, Sr9b, Sr 12, Sr 17, Sr23,
Sr24, Sr30, Sr31 and Sr 3 8) and seven stripe rust resistance genes (Yr3, Yr4, Yr6, Yr9,
in combinations in an
international wheat nursery. Genotypes carrying uncharacterised resistance for stem rust
and stripe rust against the Australian rust flora were identified for genetic analysis.
Three consistent QTL (QYr.sun-lBL, QYr.sun-2AS and QYr.sun-3BS) were demonstrated to condition high level of adult plant stripe rust resistance in Sentinel.
QYr.sun-1 BL, QYr.sun-2AS and QYr.sun-3BS explained on an average 18.0%, 15.6%
and 10.6% variation in stripe rust response, respectively. Additive nature of three QTL
to condition high level of stripe rust resistance was demonstrated through comparison of
recombinant inbred lines (RILs) carrying these QTL in all different combinations.
Detailed characterisation of these loci will be performed.
Stem rust tests on F3 populations involving Sr39 on a large and a shortened
Aegilops speltoides translocation with Sr36 on a Triticum timopheevi segment showed
complete repulsion linkage. The molecular cytogenetic analysis however indicated that
these can be recombined using large F2 population.
Significant variation for water-use efficiency related physiological traits was
observed among wheat landraces. Genotypes with low and high mesophyll conductance,
stoinatal conductance and other physiological attributes will be useful in designing
crosses to achieve high water-use efficiency in future wheat cultivars.