The bmr-12 mutation in sorghum (Sorghum bicolor) differentially affects plant defense traits and decreases establishment and activity of sugarcane aphid (Melanaphis sacchari)

Increased development of resistance to chemical insecticides from insect pests, rising global temperatures, and off-target effects on beneficial insects are moving integrated pest management toward relying on effective, sustainable strategies with the ultimate goal of reducing agricultural loss to insects. bmr-12 (brown mid rib) is a plant trait in sorghum (Sorghum bicolor) resulting from a mutation to the lignin biosynthesis pathway in which loss of caffeic acid O-methyltransferase (COMT) activity leads to the production of less lignin compared to wild type. Although previous studies have shown that bmr can differentially affect fall armyworm (Spodoptera frugiperda), a major chewing herbivore in sorghum, its potential effects against sucking herbivores are poorly understood. Sugarcane aphid (Melanaphis sacchari) has significantly reduced sorghum production throughout the southern United States and is becoming increasingly difficult to mitigate. In this study, we investigate how bmr-12 affects sorghum physiology, morphology, physical and chemical defenses, and their subsequent impact on sugarcane aphid establishment and performance. Our results using wildtype (RTx430), bmr (bmr-12), and overexpressed (11A) cultivars show that bmr-12 sorghum significantly decrease activity and ability of sugarcane aphid to reproduce, alongside a significant difference in physiology, morphology, and defense traits amongst cultivars. These findings present an unexplored, yet effective, method of sustainable pest management to be further pursued.