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. The precursors and derivatives of jasmonic acid (JA) contribute to plant protective immunity to insect attack. To understand the role of jasmonates on aphid biology, we used a sorghum multiseeded (msd) mutant, msd3, which encodes the major plastidial 18:2 desaturase, that reduces jasmonic acid (JA) synthesis. We utilized a blend of molecular biology, ecological, electrophysiological and metabolomics techniques to understand the underlying resistance mechanism(s). We found that aphids preferred to settle over mutant plants at early time points. But, at later time points, sorghum plants impaired in JA synthesis provide enhanced resistance to SCA by affecting aphid growth and reproduction negatively. Monitoring of aphid feeding behavior using electropenetrography, a technique to unveil feeding process of piercing-sucking insects, revealed that JA hormone manipulates aphid feeding duration on plants. Digging deep into mechanisms, we found that JA alter nutrition/sugar levels in plants that were confirmed to impact aphid reproduction adversely upon in vitro testing. This hormone has a more complex relationship to aphid biology than anticipated. Uncovering the underlying sorghum defense mechanisms against aphids could significantly accelerate the development of novel pest management solutions such as biologicals.
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