Creation of new rice germplasm with cross-resistance to auxin herbicides picloram and dicamba by genome editing of OsAFB4

Haonan Wei, Dongling Li, Kexin Xie, Siying Lou, Guojun Dong, Fu Guo, Guiwei Lian, Xiangjian Pan, Zhanghui Zeng, Ning Han, Zhenyu Gao & Hongwu Bian

Theoretical and Applied Genetics; October 26 2025; vol. 138; article 292

Key message

Genome Editing of OsAFB4 in rice cultivar Jiahe212 confers cross-resistance to synthetic auxin herbicides picloram and dicamba without reducing grain yield, providing a novel germplasm for herbicide-resistant rice breeding.

Abstract

Synthetic auxin herbicides (SAHs) are widely employed in global agriculture owing to low toxicity and high efficiency in weed management. Mutations in OsAFB4, an AUXIN SIGNALING F-BOX gene, led to specific resistance to SAH picloram in rice. However, potential application of OsAFB4 modification for resistance to other SAHs and its effect on agronomic traits in rice remain uncharacterized. In this study, we employed CRISPR/Cas9-mediated genome editing to generate OsAFB4 mutations in the elite commercial rice cultivar Jiahe212 (JH212). Hydroponic-culture experiments showed that Osafb4 mutant lines exhibited significant resistance to both SAHs: picloram and dicamba. Promoter activity assays using a pOsAFB4:GUS reporter line revealed that SAH treatments induced significant upregulation of GUS expression specifically in shoot apices. Under picloram or dicamba treatment, expressions of OsIAA1, OsIAA3, OsIAA9 and OsIAA20 were significantly upregulated in wild-type plants, while remarkably suppressed in Osafb4 mutants, revealing a critical role for OsAFB4 in regulating auxin-responsive IAA genes during OsAFB4-mediated sensitivity to SAH. Selected for field trials, the Cas9-free Osafb4-13 mutant line exhibited robust resistance to both picloram and dicamba without reducing grain yield compared to untreated controls. This study provides a new cross-herbicide-resistant rice germplasm without reducing grain yield by targeted editing of OsAFB4.

See https://link.springer.com/article/10.1007/s00122-025-05068-7