Professor University of Nebraska Lincoln, Nebraska
Sorghum (Sorghum bicolor) is one of the most important monocot crops cultivated worldwide and known for its versatility as a food, forage, and bioenergy crop. Sugarcane aphid (SCA; Melanaphis sacchari Zehntner) is considered a major threat to sorghum production, which severely damages the plant by sucking sap from leaves, thereby reducing its photosynthetic ability. Although several studies have been focused on the identification of sorghum resistant/tolerant varieties to SCA, very little is known about molecular mechanisms underlying sorghum resistance to SCA. Sorghum SC265, previously identified as a SCA-resistant genotype among the sorghum nested association mapping founder lines, transiently increased jasmonic acid (JA) at early stages of aphid feeding and deterred aphid settling. We utilized sorghum JA-deficient plants to understand the role of JA in sorghum-SCA interactions. Our results showed that JA deficiency promoted aphid settling, however, it also reduced aphid feeding from the phloem sap and curtailed the SCA population. Exogenous application of JA caused enhanced feeding and aphid proliferation on JA-deficient plants, suggesting that JA promotes aphid growth and development. SCA feeding on JA-deficient plants altered the sugar metabolism and enhanced the levels of fructose and trehalose compared with wild-type plants. Furthermore, aphid artificial diet containing fructose and trehalose curtailed aphid growth and reproduction. Our findings underscore a previously unknown dichotomous role of JA, which may have opposing effects by deterring aphid settling during the early stage and enhancing aphid proliferative capacity during later stages of aphid colonization on sorghum plants.
