Abstract
Sorghum (Sorghum bicolor) plays a critical role in global agriculture, serving as a staple food source and contributing significantly to various industries. However, sorghum cultivation faces significant challenges, particularly from pests like the sugarcane aphid (SCA), which can cause substantial damage to crops. In this study, we investigated the role of the caffeoyl coenzyme-A O-methyltransferase (CCoAOMT) gene in sorghum defense against SCA. Feeding by SCA induced the expression of the SbCCoAOMT gene, which is involved in the monolignol biosynthesis pathway. Aphid no-choice and choice bioassays revealed that SbCCoAOMT overexpression in sorghum resulted in reduced SCA reproduction and decreased aphid settling, respectively, compared to wild-type (RTx430) plants. Furthermore, electrical penetration graph (EPG) studies revealed that SbCCoAOMT overexpression restricts aphid feeding from the sieve elements. SCA feeding also induced the accumulation of lignin in sorghum wild-type and SbCCoAOMT overexpression plants. Moreover, artificial diet aphid feeding bioassays with hydroxycinnamic acids, ferulic and sinapic acids, showed direct adverse effects on SCA reproduction. Our findings highlight the potential of genetic modification to enhance sorghum resistance to SCA and emphasize the importance of lignin-related genes in plant defense mechanisms. This study offers valuable insights into developing aphid-resistant sorghum varieties and suggests avenues for further research on enhancing plant defenses against biotic stresses.