Abstract
Restriction fragment length polymorphisms (RFLPs) in the nuclear genome were used to assess genetic diversity among cultivated open-pollinated populations (OPs) of bulb onion (Allium cepa L.). Twenty OPs of contrasting day-length responses [long (LD) and short (SD) day] were examined with 104 random cDNA probes and two to four restriction enzymes. Sixty-one probes detected polymorphisms among the OPs for at least one restriction enzyme. Parsimony and cluster analyses were completed and no distinct grouping was observed between LD and SD OPs. Parsimony analysis generated a consensus tree that grouped all but two LD OPs and their relationships to the SD OPs were not resolved. Cluster analysis grouped all but three LD OPs and the distances from that group to the others were not greater than those among LD or SD OPs. These results suggest that LD and SD onions do not represent distinct germplasm sources and LD OPs possess a more narrow genetic background. The paucity of unique fragments among OPs indicates that phenotypic variation, e.g., day-length response or bulb color or shape, does not reflect diverse sources of germplasm.
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