AN EVALUATION OF THE UTILITY OF SSR LOCI AS MOLECULAR MARKERS IN MAIZE (ZEA-MAYS L) - COMPARISONS WITH DATA FROM RFLPS AND PEDIGREE

The utility of 131 simple sequence repeat (SSR) loci to characterize a nd identify maize inbred lines, validate pedigree, and show associatio ns among inbred lines was evaluated using a set of 58 inbred lines and four hybrids. Thirteen sets of inbred parent-progeny triplet pedigree s together with four hybrids and their parental lines were used to qua ntify incidences of scoring that departed from expectations based upon simple Mendelian inheritance. Results were compared to those obtained using 80 restriction fragment length polymorphism (RFLP) probes. Over all inbred triplets, 2.2% of SSRs and 3.6% of RFLP loci resulted in p rofiles that were scored as having segregated in a non-Mendelian fashi on. Polymorphic index content (PIG, a measure of discrimination abilit y) values ranged from 0.06 to 0.91 for SSRs and from 0.10 to 0.84 for RFLPs. Mean values for PIC for SSRs and RFLPs were similar, approximat ely 0.62. However, PIC values for nine SSRs exceeded the maximum PIC f or RFLPs. Di-repeats gave the highest mean PIC scores for SSRs but thi s class of repeats can result in ''stutter'' bands that complicate acc urate genotyping. Associations among inbreds were similar for SSR and RFLP data, closely approximating expectations from known pedigrees. SS R technology presents the potential advantages of reliability, reprodu cibility, discrimination, standardization and cost effectiveness over RFLPs. SSR profiles can be readily interpreted in terms of alleles at mapped loci across a broad range of maize germ plasm. Consequently, SS Rs represent the optimum approach for the identification and pedigree validation of maize genotypes compared to other currently available me thods.