--J. T. Gerdes and W. F. Tracy

A study was conducted to determine the diversity of 43 historically important sweet corn inbred lines. The 43 sweet corn inbreds, along with three dent inbreds (A635, W64A, and W182E), were subjected to RFLP analysis. Seventy-one probes distributed throughout the genome were used. In addition, the inbreds were scored for 22 morphological traits in a replicated field trial. Both data sets were analyzed using a hierarchical clustering technique. These results were compared to the known pedigrees of the inbreds.

Three major clusters were seen in the RFLP cluster analysis. The three dent inbreds formed the smallest and most distinct group. The second and largest cluster contained most of the yellow sweet corn inbreds. This agrees with the pedigrees of these inbreds in that nearly all of the yellow inbreds contain some Golden Bantam germplasm. The third cluster contained the Evergreen and Country Gentleman inbreds. This was unexpected in that the pedigrees of these varieties show no common ancestors. Several inbreds showed affinity to both sweet corn clusters. This agreed with their pedigrees which show that these inbreds were the result of crosses between varieties represented in the two clusters. In addition, some of the inbreds did not fit into any of the clusters. Most of these inbreds contain diverse or unknown germplasm, and some have been important in sweet corn breeding.

The morphological clustering analysis showed less distinct clusters. There was a general gradient of tall, late maturing inbreds to short, early maturing inbreds. A few of the associations seen in the RFLP analysis were also seen in the morphological analysis particularly with the most closely related inbreds. (The authors wish to thank the Agrigenetics RFLP Mapping Group for their assistance in RFLP data collection and analysis. Agrigenetics Corporation, Madison, WI.)

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