The effect of different height reducing genes on the early growth of wheat

Abstract

Genes that reduce height without compromising seedling vigour or coleoptile length have great potential for wheat improvement. We therefore investigated the effects of various reduced height (Rht) genes on the early stages of plant development, using a combination of near isogenic, recombinant, mutant and wild type comparisons. Gibberellin (GA) insensitivity caused by Rht-B1b or Rht-D1b was associated with reduced leaf elongation rate and coleoptile length. Similar results were found for two other sources of dwarfing, Rht11 and Rht17. We found one class of Rht genes (e.g. Rht8) which had no effect on coleoptile length, leaf elongation rate or responsiveness to GA, indicating that these dwarfing genes may act later in wheat development to reduce height and increase harvest index, without affecting early growth. A third class of Rht genes was found in three durum backgrounds. These had reduced coleoptile lengths and leaf elongation rates, but had a greater response to GA than the corresponding tall varieties. We discuss these results in relation to the possible mechanisms underlying the reduction in height and the suitability of the different Rht genes for wheat improvement.

Competitive ability of wheat in conventional and organic management systems: A review of the literature

“…This variation may indicate that some undesirable characteristics are not common to all semidwarf varieties and may be controlled by specific genes. This, and the use of a GA-sensitive dwarfing gene (Rht8) that has minimal pleiotropic effects on other plant characteristics, may create the possibility for the modification of undesirable traits through breeding (Gale and Youssefian 1985;Worland and Snape 2001;Ellis et al 2004). …”

Effects of Gibberellic Acid Responsive Dwarfing Gene <i>Rht9</i> on Plant Height and Agronomic Traits in Common Wheat

“…Rht4, Rht5, Rht9, Rht12, Rht13, Rht14 and Rht18) that reduce plant height by as much as 50% when compared with tall-parental or nearisogenic controls [17][18][19][20]. However, they are seemingly neutral in their effects on coleoptile length and seedling vigor [17,21,22]. Coleoptile length for progenies derived from Rht8 and Rht9 donors is generally reduced (7 to 13%) but is still 47% longer than that of Rht-B1b and Rht-D1b controls on average [16].…”

“…Several studies have been conducted to demonstrate the potential of Rht8 in the development of semi-dwarf, long coleoptiles wheat targeted at sowing depths exceeding 100 mm [11,14]. Rht8 has a smaller effect on height reduction (8-12%) than the GAI ones Rht-B1b, Rht-B1c and Rht-D1b [13,17,18]. Rht8 allele has been shown to reduce plant height and increase carbon-partitioning in grains to increase the grain number and yield [13].…”

“…Replacement of the Rht-B1b and Rht-D1b GAI-dwarfing alleles with alternate gibberellic acid-responsive (GAR) dwarfing genes shows its potential in reducing plant height without compromising seedling vigor [14][15][16][17]. Several studies have been conducted to demonstrate the potential of Rht8 in the development of semi-dwarf, long coleoptiles wheat targeted at sowing depths exceeding 100 mm [11,14].…”

“…In addition to Rht8, there are some other major GAR dwarfing genes (e.g. Rht4, Rht5, Rht9, Rht12, Rht13, Rht14 and Rht18) that reduce plant height by as much as 50% when compared with tall-parental or nearisogenic controls [17][18][19][20]. However, they are seemingly neutral in their effects on coleoptile length and seedling vigor [17,21,22].…”