Quantitative trait loci for soybean seed yield in elite and plant introduction germplasm

Genetic improvement for yield in soybean [Glycine max (L.) Merr.] has been accomplished by breeding within a narrow elite gene pool. Plant introductions (PIs) may be useful for obtaining additional increases in yield if unique and desirable alleles at quantitative trait loci (QTL) can be identified. The objectives of the study were to identify QTL for yield in elite and PI germplasm and to determine if the PIs possessed favorable alleles for yield. Allele frequencies were measured with simple sequence repeat (SSR) markers in three populations, designated AP10, AP12, and AP14, that differed in their percentage of PI parentage. AP10 had 40 PI parents, AP12 had 40 PI and 40 elite parents, and AP14 had 40 elite parents. Four cycles of recurrent selection for yield had been conducted in the three populations. Allele frequencies of the highest-yielding C4 lines in the three populations were compared with the parents used to form the populations of the initial cycles. Allele flow was simulated to account for genetic drift. Fifty-four SSRs were associated with 43 yield QTL. Seven of the QTL had been identified in previous research. Sixteen favorable marker alleles were unique to the PI parents. The genes associated with the unique PI alleles merit further investigation for their potential to increase yield of soybean cultivars.