Phalaris minor resistance to herbicides is mainly due to:

Correct option is A

· Phalaris minor (littleseed canary grass) in wheat has evolved ACCase target-site resistance to clodinafop, fenoxaprop (Aryloxyphenoxypropionate herbicides).
Why other options are wrong
· (b) ALS mutation → resistance to sulfonylureas, not major mechanism in Phalaris minor in India.
· (c) PS-II resistance → seen in Amaranthus/Chenopodium to atrazine, not Phalaris minor.
· (d) EPSPS mutations → glyphosate resistance (Conyza), not relevant here.