The Use of Molecular Markers for Determining Genetic Purity of Open Pollinated Maize Varieties.

Most countries in sub-Saharan Africa grow open pollinated maize varieties (OPVs) because seed of maize OPVs can be recycled for several seasons with minimal effects on yield due to inbreeding as compared to hybrids. However, OPVs are heterogeneous, and some local seed suppliers attempt to take advantage of this to adulterate seed bags with cheaper food grain.  If smallholder farmers purchase and sow these kernels, it will result in poor plants stands and low grain yields. The objectives of this study were to follow up on a bulked DNA fingerprinting method which can detect such mixing or mislabelling of OPVs, and to determine the level of genetic purity among the 61 seed lots of ZM521, a popular African OPV, derived from various sources. From each seed lot, 20 seeds were randomly selected and sown for DNA extraction, and equal amounts of DNA were mixed from each seedling. The bulked DNA was used for simple sequence repeat (SSR) analysis. Fifteen SSR markers were used to determine the genetic purity of the various seed lots of ZM521. The 61 seed lots grouped according to the source of foundation seed from which each seed lot was derived, and genetic divergence was large between the groups.  Within group purity was difficult to determine, suggesting that more markers (up to the 45 originally suggested for this procedure) are needed to determine the variation within each group.