Genetic effects of Rht-B1b and Rht-D1b dwarfing alleles on plant height and agronomic traits of bread wheat (Triticum aestivum L.) breeding lines

Abstract

Plant height is an important agronomic trait related to plant architecture and grain yield in wheat. We investigated the effects of the gibberellic acid (GA)-insensitive Rht-B1b and Rht-D1b semi-dwarfing alleles in a set of 599 F4:5 spring wheat breeding lines grown in rainfed and supplemental irrigation conditions at Setif semi-arid high plateaus region (Algeria). Genotyping of diagnostic markers was performed using Kompetitive Allele Specific PCR assays. The Rht-B1b mutant allele was present in 66% of the evaluated lines, while the Rht-D1b allele was found only in 8% of the lines. Relative to wild-type, Rht-B1b or Rht-D1b alone reduced plant height by 16.0 and 16.3% in rainfed, and by 20.7 and 21.8% in irrigated environments, respectively. The two dwarfing alleles when combined decreased height by 39.3 and 56.6% in rainfed and irrigated conditions, respectively. The semi-dwarf breeding lines generally outperformed the tall genotypes for yield and yield components including the number of grains per spike and harvest index irrespective of environment. Variation in heading date under the influence of dwarfing alleles has not been found. In addition, above-ground biomass was reduced in most of the short statured lines, compared to their tall counter parts across environments. We also demonstrate clear yield and yield components penalty for Rht-B1b + Rht-D1b double dwarf backgrounds.