RANDOMLY AMPLIFIED POLYMORPHIC DNA IN BULB ONION AND ITS USE TO ASSESS INBRED INTEGRITY

Commercial bulb-onion (Allium cepa L.) growers often complain that hyb rids they have grown successfully for a few years fail to perform at t he expected level. Inbreds used to produce hybrid-onion seed rarely ha ve been self-pollinated for more than two generations and retain a hig h level of heterozygosity. Over time, selection, drift, or contaminati on of inbreds may contribute to disappointing hybrid performance. We i dentified randomly amplified polymorphic DNA (RAPD) between two inbred onion lines, demonstrated their Mendelian inheritance, and tried to d istinguish among and examine changes in independently maintained, publ icly released inbred lines of onion. We observed poor agreement betwee n data sets based on genetically characterized and uncharacterized RAP D markers. Our analyses used only genetically characterized RAPD marke rs and revealed that contamination, in addition to drift and/or select ion, likely contributed to differences among independently maintained, publicly released inbreds. However, RAPD markers were not able to dis tinguish confidently among four related inbreds. RAPD markers will be useful in Allium genetics and breeding, but identifying and characteri zing reliable polymorphisms is critical.