A close relative of wheat, jointed goatgrass (Aegilops tauschii) has been
worsening the problems of Chinese farmers. Mesosulfuron is the only
wheat-registered foliar-applied herbicide that provides control of jointed
goatgrass in China, but using it damages wheat crops. Non-transgenic wheat
varieties tolerant to imidazolinone (IMI) herbicides can help solve these
problems, but IMI herbicides remain in the soil and severely damage
sensitive crops planted months and even years later.
Researchers at the Institute of Genetics and Developmental Biology of the
Chinese Academy of Sciences (IGDB, CAS) and China Agricultural University
(CAU) generated several herbicide-tolerant wheat germplasms using base
editing to facilitate weed control in wheat fields. The wheat germplasms
harboring herbicide tolerance mutations confer tolerance to sulfonylurea-,
imidazolinone- and aryloxyphenoxy propionate-type herbicides by base editing
the acetolactate synthase (ALS) and acetyl-coenzyme A carboxylase genes of
commercial wheat cultivar Kenong199.
The mutations at wheat ALS P174 codon (TaALS-P174) endow tolerance to
nicosulfuron, a sulfonylurea herbicide with a relatively low risk to
subsequently planted crops. The mutations at both the TaALS-P174 and
TaALS-G631 conferred tolerance to imazapic, an IMI herbicide, at three to
five times the field-recommended rate. The researchers also obtained
quizalofop-tolerant wheat by editing TaACCase-A1992. The researchers also
found that base editing at TaALS-P174 endowed wheat with sufficient
resistance to nicosulfuron herbicide in MS growth medium to allow selection.