The impact of the herbicide Haloxyfop-R-methyl on the development of Spartina alterniflora roots

Spartina alterniflora is a globally notorious invasive species with well-developed roots that expand rapidly, and this species seriously threatens the ecological security of coastal wetlands. This study investigated the physiological and molecular effects of the herbicide Haloxyfop-R-methyl (HPME) on the development of S. alterniflora roots. The results demonstrated that HPME rapidly inhibits the growth of S. alterniflora roots, which approached zero vitality 30 days after spraying (DAS). In the initial phase, HPME significantly enriched the pathways associated with secondary metabolites, which was a clear resistance response. At 15 DAS, the phenylpropanoid biosynthetic pathway, an important component of the defense system, was the most susceptible to HPME. The differentially expressed genes (DEGs) linked to the phenylpropanoid biosynthetic pathway were downregulated in addition to the reductions in the activities of phenylalanine ammonia-lyase and peroxidase, as well as decreases in the contents of lignin, flavonoids, and total phenolics, which indicated a weakened defense capability. Moreover, HPME significantly enriched the carbohydrate metabolism pathways and reduced the DEGs related to root development, which suggested a disruption in the physiological functions of the S. alterniflora roots. In conclusion, the herbicide HPME significantly affects the roots of S. alterniflora and may serve as an effective method for its eradication. • HPME inhibited the growth of Spartina alterniflora roots. • Root vitality tended to zero 1 month after HPME treatment. • Spartina alterniflora exhibited a resistant response to HPME in the initial phase. • Phenylpropanoid biosynthesis pathway was more susceptible to HPME. • HPME downregulated some root development-related genes ( CSLD4 , SUS6 , SUS7 , FRK2 ).