Molecular Ecology Notes (2004) doi: 10.1111/j.1471-8286.2004.00676.x © 2004 Blackwell Publishing Ltd UNCORRECTED PROOF MEN_676 Pages: 3 Proofreader: Chen Xiaoming Blackwell Publishing, Ltd. PRIMER NOTE Microsatellite DNA markers for the pea aphid Acyrthosiphon pisum M. C. CAILLAUD,* G. MONDOR-GENSON,† S. LEVINE-WILKINSON,* L. MIEUZET,‡ A. FRANTZ,‡ J. C. SIMON‡ and A. COEUR D’ACIER† * Ithaca College, Department of Biology, 165 Center for Natural Sciences, Ithaca NY 14853, USA, † Centre de Biologie et Gestion des Populations (CBGP), Campus International de Baillarguet, CS 30 016, 34 988 Montferrier sur Lez Cedex, France, ‡ UMR INRA/ ENSAR ‘Bio3P’, INRA B.P. 29, 35653 Le Rheu cedex, France Abstract Microsatellite loci were isolated from enriched partial genomic libraries of Acyrthosiphon loti and Acyrthosiphon pisum. Twenty of those loci were characterized in A. pisum. Fifteen of those loci were polymorphic. Genetic diversity varied across loci, allele repeat number ranging from two to 15, and observed heterozygosity from 0.1 and 0.96. An additional eight microsatellite loci originally isolated from other aphids but cross-priming with A. pisum showed polymorphism as well. Allele size ranged from three to 9 and observed heterozy- gosity from 0.43 to 0.84. Overall, we present 23 microsatellite loci that can be used to reveal polymorphism in pea aphids. Keywords: cross priming, dinucleotide repeats, enriched library, microsatellite, pea aphid Received 20 December 2003; revision received 12 February 2004; accepted 22 March 2004 Aphids offer a unique advantage over many other arthropod systems for the study of the genetics of complex pheno- types because they are cyclically parthenogenetic. Every aphid hybrid lineage generated by sexual reproduction can be reproduced parthenogenetically, allowing replicate phenotypic measurements of each hybrid genotype. This replication is especially important for the study of genotype – environment interaction. The pea aphid, Acyrthosiphon pisum Harris (Homoptera, Sternorrhyncha) displays multiple advantages over other aphid species for development as a genetic system and is thus quickly becoming the workhorse genetic aphid system. However, few ‘genetic’ re- sources have been developed so far. In particular, only one linkage map, based on AFLP markers, has been published (Hawthorne & Via 2001). Microsatellite markers harbour considerable length variation, are extremely abundant, and are randomly dis- tributed throughout eukaryotic genomes ( Jarne & Lagoda 1996). Consequently, they have found wide application as markers in human, mammalian, plant and invertebrate genetics, for the construction of highly informative and saturated genetic maps. Here, we characterize 23 micro- satellite loci in the pea aphid. Fifteen of those loci are new. Eight of those loci have been previously characterized in three aphid species (Simon et al . 1999, 2001; Wilson et al . 2004) and we present here the result of cross-priming tests in the pea aphid. Two separate microsatellite libraries were made. One with several genotypes of Acyrthosiphon loti L. (Homoptera, Sternorrhyncha) collected on Lotus corniculata L. plants in Montpellier (France) in 2002. One with a single genotype of A. pisum collected on Medicago sativa L. (alfalfa) in 1998 in Ithaca (NY state, USA). Genomic DNA was isolated from fresh aphids following standard procedure (Sambrook et al . 1989) and digested with Rsa I restriction enzyme. A 300 –1000 bp fraction of the digested DNA was selected on agarose gel, purified and ligated to Rsa linkers. The enrichment procedure followed the protocol from Kijas et al . (1994) based on streptavidin- coated magnetic particles (Magnesphere, Promega), with slight modifications. 5 ′ -biotinylated (CT) 10 and (GT) 10 oligo- nucleotide were used as probes. The enriched single stranded DNA was amplified using one of the Rsa linkers as primer to recover double stranded DNA. The polymerase chain reaction (PCR) products were purified and ligated into pGEM-T Easy vector (Promega), and the plasmid trans- formed into Escherichia coli supercompetent cells (XL1 blue, Correspondence: Marina C. Caillaud. Fax: + 1607 2741131; E-mail: mcaillaud@ithaca.edu