North American study on essential derivation in maize: II. Selection and evaluation of a panel of simple sequence repeat loci

Plant variety protection laws based on the 1991 revision of the Union Internationale pour la Protection des Obtentions Vegetales (UPOV) include the concept of an essentially derived variety (EDV). It is widely accepted that molecular markers can provide data to help determine EDV status. We screened publicly available simple sequence repeat (SSR) loci using a set of inbred lines, including those that have been widely used or are of historic importance to maize (Zea mays L.) breeding in the United States. As a result of that screening process we hereby publish a set of 285 SSRs that have been validated by the American Seed Trade Association (ASTA) for use in variety identification and for assistance in determining EDV status in U.S. maize. One hundred and fifty SSRs constitute the ASTA Core Set 1; additional data, if required, can be obtained by using the additional 135 SSRs. We also report on comparisons of abilities of the ASTA-designated SSRs to discriminate among and show associations among inbred lines compared with results obtained from another (partially overlapping) set of SSRs selected by the French Association of Maize Breeders (SEPROMA). There was a high correlation (R² = 0.79) for pairwise distances among a subset of 30 U.S. inbreds for SSR data obtained using the ASTA protocols compared with those obtained using the SEPROMA protocols. Consequently, there are now two published sets of protocols and procedures that can be used to assist in variety identification and in the determination of essential derivation in maize depending on circumstances and available resources.