The effects of dwarfing genes on seedling root growth of wheat

Abstract

Most modern wheat cultivars contain major dwarfing genes, but their effects on root growth are unclear. Nearisogenic lines (NILs) containing Rht-B1b, Rht-D1b, Rht-B1c, Rht8c, Rht-D1c, and Rht12 were used to characterize the effects of semi-dwarfing and dwarfing alleles on root growth of 'Mercia' and 'Maris Widgeon' wheat cultivars. Wheat seedlings were grown in gel chambers, soil-filled columns, and in the field. Roots were extracted and length and dry mass measured. No significant differences in root length were found between semi-dwarfing lines and the control lines in any experiment, nor was there a significant difference between the root lengths of the two cultivars grown in the field. Total root length of the dwarf lines (Rht-B1c, Rht-D1c, and Rht12) was significantly different from that of the control although the effect was dependent on the experimental methodology; in gel chambers root length of dwarfing lines was increased by ;40% while in both soil media it was decreased (by 24-33%). Root dry mass was 22-30% of the total dry mass in the soil-filled column and field experiments. Root length increased proportionally with grain mass, which varied between NILs, so grain mass was a covariate for the analysis of variance. Although total root length was altered by dwarf lines, root architecture (average root diameter, lateral root:total root ratio) was not affected by reduced height alleles. A direct effect of dwarfing alleles on root growth during seedling establishment, rather than a secondary partitioning effect, was suggested by the present experiments.

Methods to estimate changes in soil water for phenotyping root activity in the field

“…The panel included two sets of isogenic lines to test the effect of Rht alleles on root activity, as the literature is not clear on how different Rht alleles affect root growth and depth (e.g. Wojciechowski et al 2009;Miralles et al 1997). We compared the tall RhtC (RhtB1a) and dwarf Rht3 (Rht-B1c) near isogenic lines, allelic at the Rht-B1 locus, in a Mercia background.…”

Large root systems: are they useful in adapting wheat to dry environments?

“…As discussed above, this can be problematic. For example, Wojciechowski et al (2009) showed that the effect of Rht genes on root growth was strongly positive in gel cultures but strongly negative in soil. Potential approaches for efficient phenotyping of root traits under controlled conditions have recently been reviewed by Gregory et al (2009), who indicated significant emerging capability.…”

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

“…Root characters affect plant establishment, water and nutrient uptake in the field, especially in water limited regions. The effects of GAI Rht genes on wheat root system varied in previous studies, as little or only a slightly negative effect [35,36] and strong negative effects observed in semi dwarf wheat cultivars with GAI dwarfing genes RhtB1b and Rht-D1b [37,38]. Most works on GAR dwarfing genes indicated that less negative effects were observed on wheat root system [22].…”