EMS-induced point mutations in ALCATRAZ homoeologs increase silique shatter resistance of oilseed rape (Brassica napus)

Abstract

In Arabidopsis (Arabidopsis thaliana), the transcription factor ALCATRAZ (ALC) is involved in the control of silique tissue identity, ensuring the establishment of a separation layer that contributes to the fragility of the dry fruit. The silique structure is retained in the related crop species oilseed rape (Brassica napus), in which it causes yield losses due to seed shedding. A more robust rapeseed silique through Bnalc loss-of-function mutations was hypothesized. We demonstrated the increased silique shatter resistance of oilseed rape through Cas9-induced targeted Bnalc mutations in a previous work. However, the effect was masked by the high shatter resistance of the transformed cultivar itself. In the present study, we used a rapeseed genotype with low shattering resistance and followed an approach of random mutagenesis. We identified 23 Bnalc mutants by TILLING of an EMS-mutagenized ‘Express’ population. By measuring tensile forces necessary to disrupt mature siliques, we determined a double mutant with significantly increased shatter resistance. This mutant can readily be introduced into breeding programs.