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rAmpSeq: Using repetitive sequences for robust genotyping

Edward S. BuckleriD, Daniel C. IlutiD, Xiaoyun WangiD, Tobias KretzschmariD, Michael A. GoreiD, Sharon E. Mitchell

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Abstract summary

Claude Opus 5.5 · xhigh effort · 18 Oct 2026 · from the abstract

Primers anchored in conserved repeat sequence amplify thousands of maize middle-repetitive loci at once, with markers called from the low-copy sequence between copies for under $5 per sample.

Genomic selection and large conservation surveys hinge on per-sample genotyping cost once hundreds of thousands of individuals must be scored. This approach turns repeat families into an advantage: because the flanking sequence is conserved across many copies, one primer set amplifies over a thousand loci, and the variable low-copy sequence between copies supplies the polymorphisms, so marker count comes from multiplexing inside the amplification rather than from running more assays.

Key results

  1. ShownFour maize primer sets each recovered on the order of one to three thousand loci with adequate coverage, and a subset of those behaved as expected genetically in a cross.

    Between 1,335-3,225 good coverage loci per primer set, of which 1056 segregated appropriately in a bi-parental family. · Abstract

  2. ClaimedThe workflow is costed at under $5 per sample for hundreds to thousands of markers, combining simple DNA preparation, optimised PCR, highly multiplexed Illumina indexing and a caller written for repetitive sequence.

    The figure is stated as a platform property; the abstract gives no cost breakdown, throughput per run, or comparison with other genotyping platforms. · Abstract

  3. ClaimedThe authors expect the strategy to transfer to breeding programmes and conservation biology, where sample numbers reach the hundreds of thousands.

    Stated as prospective applicability; results are reported only for maize primer sets, with no other species or panel tested in the abstract. · Abstract

Methods, data and reproducibility

Conserved parts of repeat families were used to design PCR primers that amplify thousands of middle-repetitive regions of the maize genome; polymorphisms were then located computationally in the low-copy sequence lying between repeat copies. Genotyping combines simple DNA preps, optimised PCR, highly multiplexed Illumina indexing and a marker-calling pipeline built for repetitive sequence.

  • Loci amplified by four primer sets targeting middle-repetitive regions · maize (Zea mays ssp. mays) · n = four primer sets; 1,335-3,225 loci each
  • Bi-parental family used to check that markers segregate as expected · maize (Zea mays ssp. mays) · n = 1056 appropriately segregating loci
Methods & tools
rAmpSeq, Illumina
Limitations (2)
  • Only part of the recovered loci segregated appropriately in the test family (1056 against 1,335-3,225 loci per primer set), and the abstract does not say what happens to the rest or what the genotype error rate is. · noted in this summary
  • Evidence comes from maize alone, from four primer sets and a single bi-parental cross, with no comparison against other low-cost genotyping platforms reported here. · noted in this summary

Read this if you must genotype very large breeding or conservation panels on a tight budget and are weighing repeat-anchored multiplex amplicons against per-locus assays.

Citations
45

Abstract

Repetitive sequences have been used for DNA fingerprinting and genotyping for more than a quarter century. Now, with our knowledge of whole genome sequences, repetitive sequences can be used to identify polymorphisms that can be mapped and scored in a systematic manner. We have developed a simple, robust platform for designing primers, PCR amplification, and high throughput cloning that allows hundreds to thousands of markers to be scored for less than $5 per sample. Conserved regions were used to design PCR primers for amplifying thousands of middle repetitive regions of the maize (Zea mays ssp. mays) genome. Bioinformatic scans were then used to identify DNA sequence polymorphisms in the low copy intervening sequences. When used in conjunction with simple DNA preps, optimized PCR conditions, high multiplex Illumina indexing and a bioinformatic marker calling platform tailored for repetitive sequences, this methodology provides a cost effective genotyping strategy for large-scale genomic selection projects. We show detailed results from four maize primer sets that produced between 1,335-3,225 good coverage loci with 1056 that segregated appropriately in a bi-parental family. This approach could have wide applicability to breeding and conservation biology, where hundreds of thousands of samples need to be genotyped for very minimal cost.

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