Meiotic instability and irregular chromosome pairing underpin heat‐induced infertility in bread wheat carrying the <i>Rht‐B1b</i> or <i>Rht‐D1b</i> Green Revolution genes

Abstract

Summary Mutations in the Rht‐B1a and Rht‐D1a genes of wheat ( Triticum aestivum ; resulting in Rht‐B1b and Rht‐D1b alleles) cause gibberellin‐insensitive dwarfism and are one of the most important elements of increased yield introduced during the ‘Green Revolution’. We measured the effects of a short period of heat imposed during the early reproductive stage on near‐isogenic lines carrying Rht‐B1b or Rht‐D1b alleles, with respect to the wild‐type (WT). The temperature shift caused a significant fertility loss within the ears of Rht‐B1b and Rht‐D1b wheats, greater than that observed for the WT. Defects in chromosome synapsis, reduced homologous recombination and a high frequency of chromosome mis‐segregation were associated with reduced fertility. The transcription of TaGA3ox gene involved in the final stage of gibberellic acid (GA) biosynthesis was activated and ultra‐performance liquid chromatography–tandem mass spectrometry identified GA 1 as the dominant bioactive GA in developing ears, but levels were unaffected by the elevated temperature. Rht‐B1b and Rht‐D1b mutants were inclined to meiotic errors under optimal temperatures and showed a higher susceptibility to heat than their tall counterparts. Identification and introduction of new dwarfing alleles into modern breeding programmes is invaluable in the development of climate‐resilient wheat varieties.