Combining gibberellic acid-sensitive and insensitive dwarng genes in breeding , sesqui-dwarf wheats

Field Crops Research 127(2012)17–25

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Combining gibberellic acid-sensitive and insensitive dwarng genes in breeding , sesqui-dwarf  wheats

Combining gibberellic acid-sensitive and insensitive dwarng genes in breeding , sesqui-dwarf  wheats

Field Crops

Research

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Combining gibberellic acid-sensitive and insensitive dwarfing genes in breeding of higher-yielding,sesqui-dwarf wheats

G.J.Rebetzke ∗,D.G.Bonnett 1,M.H.Ellis 1

CSIRO Plant Industry,PO Box 1600,Canberra,ACT 2601,Australia

a r t i c l e

i n f o

Article history:

Received 24July 2011

Received in revised form 10October 2011Accepted 3November 2011

Keywords:

Yield potential Breeding

Harvest index Establishment Coleoptile

a b s t r a c t

Reductions in plant height are associated with genotypic increases in lodging resistance,harvest index and wheat yields worldwide.Historically,the largest single increase in harvest index and yield was seen in development of semi-dwarf wheats through introgression of the gibberellic acid (GA)-insensitive,Rht-B1b and Rht-D1b dwarfing alleles.A suite of GA-sensitive dwarfing genes including Rht8are also available and their neutral effects on seedling vigour suggest their potential in being deployed singly,or in combination with GA-insensitive dwarfing alleles.Five biparental and backcross populations each comprising between 44and 124progeny were developed from commercial parents varying for alleles at either the Rht-B1or Rht-D1and the Rht8dwarfing gene loci.Progeny was grown together in multiple environments,and assessed for agronomic performance and coleoptile growth.Genotypic variation was large and significant (P <0.05)for plant height,grain yield and its components,harvest index,grain number and size.Reduction in plant height for lines containing Rht8c and either Rht-B1b or Rht-D1b dwarfing alleles averaged 8and 17%,respectively.The Rht8c +Rht-B1b/D1b sesqui-dwarfs were significantly (P <0.05)shorter (−24%)and commonly higher-yielding (+6to 10%)than lines containing either dwarfing gene alone.Their higher yields reflected similar biomass but a greater harvest index (+7to 11%)and reduced lodging (−19to −32%)compared to single dwarfs.The Rht8c dwarfing allele did not appear epistatic with either Rht-B1b or Rht-D1b alleles in effects on plant growth.Coleoptile lengths were similar for sesqui-and Rht-B1b/D1b single-dwarfs and both shorter than for Rht8c and tall lines.Together with their pleiotropic effects on harvest index and availability of linked molecular markers,simultaneous selection of Rht8c +Rht-B1b or Rht-D1b sesqui-dwarfs in early generations may facilitate rapid development of high-yielding varieties targeting favourable and unfavourable environments alike.

Crown Copyright ©2011Published by Elsevier B.V.All rights reserved.

1.Introduction

The most common dwarfing genes in wheat breeding pro-grams are the GA-insensitive Rht-B1b (formerly Rht1)and Rht-D1b (formerly Rht2).These are effective in reducing plant height and have been widely adopted in wheat breeding programs since their introduction in the 1950s (Flintham et al.,1997;Bonnett et al.,2001).Their use has been associated with increased wheat yields particularly where conditions for growth are favourable (e.g.Waddington et al.,1986;Chapman et al.,2007).Height reductions arising from the presence of these genes increase yield by altering the proportion of dry matter allocated to grain (measured as harvest index),and by reducing plant lodging especially with increasing yield potential of the environment (Berry et al.,2007).The Rht-B1b and Rht-D1b genes reduce plant height by decreasing

∗Corresponding author.Tel.:+61262465153;fax:+61262465399.E-mail address:Greg.Rebetzke@csiro.au (G.J.Rebetzke).1

Currently CIMMYT Int.Apdo.,Postal 6-641,06600México,DF,Mexico.

sensitivity of vegetative and reproductive tissues to endogenous gibberellin (Keyes et al.,1989).Cell elongation is reduced,result-ing in a decreased internode length and shorter plant height.However,smaller cells also contribute to reduced seedling vigour and coleoptile length,crop water-use efficiencies (Allan,1989;Richards,1992b;Rebetzke et al.,2004;Botwright et al.,2005),and performance in environments of lower yield potential (Butler et al.,2005;Chapman et al.,2007).

In many spring wheat-regions,early-sown crops have potential to produce greater yields through increased water-use and water-use efficiency (Gomez-Macpherson and Richards,1995;Kirkegaard and Hunt,2010).However,the larger biomass with the longer duration for growth and potential for greater yields is commonly offset by increased plant height (Stapper and Fischer,1990).Har-vest index is subsequently reduced in spite of use of Rht-B1b and Rht-D1b semi-dwarf alleles (Stapper and Fischer,1990).Further,as occurs with other well-managed,high yield potential wheat crops (e.g.in irrigated,fertilised environments),semi-dwarf wheats car-rying these alleles are predisposed to lodging resulting in reduced crop yields (Stapper and Fischer,1990;Berry et al.,2007).Deployed

0378-4290/$–see front matter.Crown Copyright ©2011Published by Elsevier B.V.All rights reserved.doi:10.1016/j.fcr.2011.11.003

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