Changes in durum wheat root and aerial biomass caused by the introduction of the Rht-B1b dwarfing allele and their effects on yield formation

Abstract

This study aimed to quantify the changes in root and aerial biomass of durum wheat brought about by the introduction of the Rht-B1b dwarfing allele and their effects on yield formation. A historical series of 24 Mediterranean cultivars with allelic variants a (tall) and b (semi-dwarf) at Rht-B1 locus was tested in tubes in three greenhouse experiments and six field experiments. The dwarfing allele reduced the aerial biomass of each plant at anthesis by 7.6 % and the root by 28.1 % (25.4 %, 26.7 % and 36.0 % in the upper, middle and lower root sections, respectively). Aerial and root biomass were reduced by 27.0 g y−1 and 7 g y−1 respectively, but the relative rate of change was much greater for roots (−0.73 % y−1) than for aerial organs (−0.17 % y−1). Aerial biomass at anthesis was negatively associated with spike number, harvest index and yield in tall cultivars, but no significant relationship was found for semi-dwarf ones. The root/aerial biomass ratio was 29 % lower in semi-dwarf than in tall cultivars. In tall cultivars large aerial biomass at anthesis was detrimental to yield formation, while in semi-dwarf cultivars high aerial biomass at anthesis had no effect on yield formation.