Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/23/2017
Publication Date: 3/9/2017
Citation: Harris-Shultz, K.R., Ni, X., Wadl, P.A., Wang, X., Wang, H., Huang, F., Flanders, K., Seiter, N., Kerns, D., Meagher Jr, R.L., Xue, Q., Reisig, D., Buntin, D., Cuevas, H.E., Brewer, M., Yang, X. 2017. Microsatellite markers reveal a predominant sugarcane aphid (Homoptera: Aphididae) clone is found on sorghum in seven states and one territory of the USA. Crop Science. 57:2064-2072.

Interpretive Summary: Since 2013, the sugarcane aphid (Melanaphis sacchari) on sorghum has been rapidly spreading from state to state in the southern United States and in 2016 reached 19 states. These aphids often become so abundant in numbers that most sorghum fails to develop the main heads and for many, plant death occurs. There is uncertainty if there are multiple sugarcane aphid genotypes on sorghum in the U.S. or if all aphids are one genotype. Thus in this study, high throughput sequencing was conducted for the sugarcane aphid and 1.44 Gb of nucleotides were generated. From this data, as well as a previous study, 52 microsatellite markers were utilized to genotype 48 samples from 17 locations across 7 states and one U.S. territory. All samples were one genotype with the exception of a single sample collected from Sinton, TX which had the predominant genotype as well as another genotype. Thus the invasive sugarcane aphid is spreading on sorghum in the U.S. as primarily one “superclone”. Knowledge of the number of sugarcane aphid genotypes is important for identifying resistant sorghum plants and for insecticide use.

Technical Abstract: The sugarcane aphid, Melanaphis sacchari, has become a serious pest causing severe economic losses to sorghum grown in the southern United States (U.S.). Since its original detection in four states in 2013, M. sacchari on sorghum has now, for 2016, spread to 19 states. The presence of one or multiple genotypes on sorghum in the U.S. has not yet been established. In this study, genome sequencing of M. sacchari was used to develop microsatellite markers. A total of 8,665,267 reads and 1.44 Gb of nucleotide sequences were generated and 78.4% of the reads were from M. sacchari. M. sacchari DNA from 48 samples from 17 locations across 7 states and one U.S. territory was polymerase chain reaction (PCR) amplified using 38 newly created microsatellite markers as well as 14 published microsatellite markers. Genotyping with the 52 microsatellite markers indicated that the samples of M. sacchari on sorghum were all one genotype with the exception of a single sample collected from Sinton, TX, which had the predominant genotype as well as another genotype. Genotyping of the aphid samples with 12 microsatellite markers for Buchnera aphidicola, the obligate aphid symbiont, had nearly identical results. The invasive M. sacchari on sorghum appears to be spreading in the U.S. on sorghum as primarily one asexual clone.