DNA fingerprinting of open-pollinated maize seed lots to establish genetic purity using simple sequence repeat markers

Abstract

Maize (Zea mays L.) plays a dominant role in farming systems in sub-Saharan Africa (SSA). There has been a fourto- five-fold increase in the number of seed companies in SSA in the last decade, and yet more than half of smallholder farmers still grow traditional and unimproved varieties. The adoption of open-pollinated varieties (OPVs) and hybrids is around 44% of all farmers in SSA. Open-pollinated varieties are heterogeneous, and some local seed suppliers may attempt to take advantage of this to adulterate seed bags with cheaper food grain. This study sought to use a bulked DNA fingerprinting method to determine the identity and level of genetic purity among 35 seed lots of ZM521, a popular African OPV, maintained by various sources and the foundation seed source of ZM521 maintained by CIMMYT. From each seed lot, 20 individuals were bulked and analysed with 15 fluorescently labelled simple sequence repeat markers on an automatic DNA sequencer, allowing allele frequency to be determined from the bulk using peak intensity. The 35 seed lots grouped according to the source of foundation seed from which each seed lot was derived, and large genetic divergences were observed among different OPVs and hybrids.

Keywords: DNA fingerprinting, maize seed, open-pollinated varieties, simple sequence repeat, Zea mays