Loss of Liguleless1 ( LG1 ) Function Enhances Sorghum Resistance to Sugarcane Aphids

Sorghum ( Sorghum bicolor L.) is a globally important crop used for food, fodder, and biofuel production; however, its productivity is severely constrained by insect pests such as sugarcane aphid (SCA). Previous studies have shown that loss of LIGULELESS1 ( LG1 ) function activates jasmonate signaling and enhances maize resistance to corn leaf aphids. Here, we investigated the role of LG1 in sorghum defense against SCA. Aphid no-choice bioassays revealed that loss of LG1 significantly reduced aphid settling and reproduction. EPG analysis further revealed that lg1 mutant significantly increased aphid probing/pathway phase while reducing sieve element phase duration, suggesting impaired phloem feeding and altered aphid feeding behavior on lg1 plants. Gene expression analysis using RT-qPCR showed that SCA feeding suppressed key jasmonic acid (JA) signaling genes in lg1 plants, while hormone profiling revealed enhanced salicylic acid (SA) accumulation and altered JA and abscisic acid responses in lg1 plants following infestation. Notably, this shift is consistent with the well-established antagonistic crosstalk between JA and SA pathways, where activation of SA signaling often suppresses JA-mediated responses. Growth-associated hormones were also differentially affected by SCA feeding. Together, these results demonstrate that LG1 modulates hormone-dependent defense responses in sorghum and represents a promising target for improving resistance to aphid pests.