Microsatellite Markers Reveal a Predominant Sugarcane Aphid (Homoptera: Aphididae) Clone is Found on Sorghum in Seven States and One Territory of the USA

The sugarcane aphid (Melanaphis sacchari) has become a serious pest causing severe economic losses to sorghum [Sorghum bicolor (L.) Moench] grown in the southern United States. Since its original detection in four states in 2013, M. sacchari on sorghum has now, in 2016, spread to 19 states. The presence of one or multiple genotypes on sorghum in the United States 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 79.6% of the reads were from M. sacchari. Melanaphis sacchari DNA from 46 samples from 17 locations across seven states and one US 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 United States on sorghum as primarily one asexual clone. K. Harris-Shultz, X. Ni, and H. Wang, USDA-ARS, Crop Genetics and Breeding Research Unit, 115 Coastal Way, Tifton, GA 31793; P.A. Wadl, USDA-ARS, US Vegetable Laboratory, 2700 Savannah Highway, Charleston, SC 29414; X. Wang, USDA-ARS, Southern Plains Agricultural Research Center, 2881 F&B Rd., College Station, TX 77845; F. Huang, Louisiana State Univ. AgCenter, 404 Life Science Building, Baton Rouge, LA 70803; K. Flanders, Auburn Univ., 201 Extension Hall, Auburn Univ., AL 36849; N. Seiter, Univ. of Arkansas System Division of Agriculture, Southeast Research and Extension Center, PO Box 3508, Monticello, AR 71656; D. Kerns, Louisiana State Univ., Macon Ridge Research Station, 212A Macon Ridge Rd., Winnsboro, LA 71295; R. Meagher, USDA-ARS, Insect Behavior and Biocontrol Research Unit, 1600-1700 SW 23rd Dr., Gainesville, FL 32608; Q. Xue, Texas A&M AgriLife Research, 6500 Amarillo Blvd W. , Amarillo, TX 79106; D. Reisig, North Carolina State Univ., The Vernon James Research & Extension Center, 207 Research Station Rd., Plymouth, NC 27962; D. Buntin, Univ. of Georgia Griffin Campus, 1109 Experiment St., Griffin, GA 30223; H.E. Cuevas, USDA-ARS, Tropical Agriculture and Research Station, 2200 P.A. Campos Ave Suite 201, Mayaguez, PR 00680; M.J. Brewer, Texas AgriLife Research–Corpus Christi, 10345 Hwy 44, Corpus Christi, TX 78406; X. Yang, Univ. of California Davis, 1636 E. Alisal St., Salinas, CA 93905. Received 20 Dec. 2016. Accepted 4 Apr. 2017. *Corresponding author (Karen.Harris@ars. usda.gov). Assigned to Associate Editor Tejinder Mall. Abbreviations: GC, guanine-cytosine; MLL, multilocus lineages; PCR, polymerase chain reaction; SSR, simple sequence repeat; UPGMA, unweighted pair group method with arithmetic mean. Published in Crop Sci. 57:2064–2072 (2017). doi: 10.2135/cropsci2016.12. 1010 © Crop Science Society of America | 5585 Guilford Rd., Madison, WI 53711 USA All rights reserved. Published May 18, 2017