Accumulation of mutations in the homoeologs causes suppression of anther extrusion with altered spike and culm development in hexaploid wheat.

Unlabelled: Cleistogamy or closed flowering is a widely used trait in barley () breeding because it reduces the risk of fungal infection in florets at anthesis. Cleistogamy in barley is caused by a point mutation within the microRNA172 (miR172) target site of the gene, which encodes the Apetala2 (AP2) transcription factor. Because cleistogamy is not apparent in cultivars of hexaploid wheat (), a strategy to develop cleistogamous wheat was proposed by inducing point mutations in all three homoeologs, which are the wheat orthologs of barley . In this study, we investigated the effects of miR172 target site mutations on wheat cleistogamy using double mutants by combining three previously obtained mutant alleles (, and ) in a near-isogenic background. The allele had the greatest effect on reducing the anther extrusion rate and lodicule size compared with the other two mutant alleles. The double mutant containing the and alleles had a much greater suppression of anther extrusion by reducing the lodicule size than the single mutant, suggesting cumulative effects of the two mutant alleles. In addition, both single and double mutants exhibited compact spikes and shorter plant heights due to reduced rachis and culm internodes in the upper parts. The presence or absence of the wild-type homoeolog had no significant effect on phenotype. This study provides insights into the cumulative effects of mutant alleles in suppressing open flowering and provides a basis for further research on the development of complete cleistogamy in hexaploid wheat.

Supplementary Information: The online version contains supplementary material available at 10.1007/s11032-024-01458-9.