8th INTERNATIONAL WHEAT CONFERENCE

versus sister lines carrying Rht-B1b or Rht-D1b. Interestingly the screenings levels of
Rht4 and Rht13 lines were significantly lower than Rht-B1b and Rht-D1b sister lines
while Rht5 and Rht8 were equivalent and the strongest dwarfing gene, Rht12, associated
with a significant increase in screenings %. Results of our studies on effects of GAresponsive
dwarfing genes on early growth, yield and grain size strongly support the
adoption of Rht4, Rht5 and Rht13 as replacements for Rht-B1b and Rht-D1b in wheat
breeding programs. These genes have been mapped (Ellis et al 2005) which should support
development of closely-linked markers for use in routine selection. The availability
of perfect markers for Rht-B1b and Rht-D1b (Ellis et al. 2002) is equally or even more
important to allow selection against these almost ubiquitous genes. The Rht4, Rht5 and
Rht13 dwarfing genes are now being introduced into CIMMYT’s wheat breeding efforts.
References
Ellis MH, Spielmeyer W, Gale K, Rebetzke GJ, Richards RA. 2002. Perfect markers for
the Rht-B1b and Rht-D1b dwarfing mutations in wheat (Triticum aestivum L.). Theor.
Appl. Genet. 105, 1038-1042.
Ellis MH, Rebetzke GJ, Azanza F, Richards RA, Spielmeyer W, Richards RA. 2005.
Molecular mapping of giberellin responsive dwarfing genes in bread wheat. Theor. Appl.
Genet. 111, 423-430.
Mathews KL, Chapman SC, Trethowan R, Singh RP, et al.. 2006. Global adaptation of
spring bread and durum wheat lines near-isogenic for major reduced height genes. Crop
Sci. 46, 603-613.
Rebetzke GJ, Richards RA, Fettell NA, Long M, et al. 2007. Genotypic increases in coleoptile
length improves wheat establishment, early vigour and grain yield with deep sowing.
Fld Crops Res. 100, 10-23.
Richards, R.A. 1992. The effect of dwarfing genes in spring wheat in dry environments I.
Agronomic characteristics. Aust. J. Agric. Res. 43, 517-527.
156