212
8.6 Conclusions
There is extensive variability for resistance to disease and pests and value added
traits in wild wheats and species related to them. Even in the primary and secondary
gene pools covered in this text there is extensive variability. There is much more in
the tertiary gene pool. The variability in the primary and secondary gene pool is
readily accessible. Genes can be transferred by simple crossing then backcrossing.
Embryo rescue needs to be used in many combinations. Of the totals of genes that
have been identifi ed and transferred to wheat relatively few have been deployed.
The deployment is currently being accelerated. This may be attributed to more
effort in developing molecular markers for the genes and using these to “pyramid”
the genes. Technologies such as doubled haploids are being employed to permit
selection of multiple genes in reduced population sizes. Pyramids might consist of
multifunctional genes such as Lr34 , Sr33 , Sr42 , Fhb1 (Zhang et al. 2014 ) or multi-
ple genes for one function such as Sr33 , Sr36 , Sr42 , and Sr43 (Jin et al. 2014 ). In
the case of the latter, it was produced to give prolonged resistance to stem rust race
Ug99. Three of the four genes involved in that pyramid have been introgressed from
alien sources.
Acknowledgements The author wishes to acknowledge the excellent input and assistance pro-
vided by Dawn T. Chi in typing, formatting the manuscript and arranging the fi gures and tables.
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