Antixenosis to the Sugarcane Aphid [Melanaphis sacchari (Zehntner) (Aphididae)] in 16 Graminous Species By Greg Wilson Graduate Assistant for Dr. David Kerns (2016) Macon Ridge Research Station, Winnsboro LA Department of Entomology, Louisiana State University

Thesis Objectives - Supporting Research Needs …use of resistant cultivars is an effective management technique for aphids (Smith 2005) and since the specificity of resistance towards closely related aphid biotypes is important (Fartek 2012), then identifying bases of resistance for known genotypes will aid in improving the applicability of host plant resistance against M. sacchari (Akbar 2010). …a need to assess the role of antixenosis and colonization in genotypic reaction against M. sacchari to identify the lines with different mechanisms of resistance to this pest (Sharma at. al 2014). …data on the identity, origin, and biological cycle of the M. sacchari / sorghi complex currently are insufficient and contradictory, and recommend further laboratory and field studies on such topics as the holocycle, morphometric and molecular characterization of the species or biotypes, host transfer, and range of host plants (Rodríguez-del-Bosque 2015). A haplotype is a group of genes within an organism that was inherited together from a single parent

Methods: Antixenosis for Haplotype A (March 2016) RCB 16 spp. (8 spp. x 3 reps x 2 groups) 10 seeds per row Greenhouse temperatures 80-87°F Sorghum isolates infested (5th leaf stage) Shaking 250 aphids inside of box lid Population counts and damage scores (1-9) at 4 time points: 2 and 7 DAI 1st row average phytotoxicity score is 7-8 2nd row average score a 7-8

Results: Antixenosis

Results: Antixenosis

Discussion / Conclusion Significant outcomes from our studies for Haplotype A Discussion / Conclusion Preference for Sorghum over Sugarcane Supported by reproductive potential and no-choice testing Some grasses in the genera Echinochloa, Miscanthus, Pennisetum can act as temporary reservoirs Sugarcane [S] is an LSU experimental line which showed true field susceptibility to Haplotype A Potential to isolate and identify susceptibility mechanisms for sorghum since grasses are phylogenetically similar Ongoing: Antixenosis test of resistant and susceptible hybrids