On the origin of the inbred line B52 --M. Lee, W.A. Russell, A.E. Melchinger, and W.L. Woodman
Inbred line B52 has attracted considerable attention by maize breeding programs because of its high level of resistance to sheath collar feeding and stalk tunnelling by second generation larvae of European corn borer (Ostrinia nubilalis H.). There have been numerous requests regarding the source population or origin of this line; unfortunately, such records do not exist. In this report, we would like to present what we do know about relationships to other inbred lines.

In 1952 Dr. G.F. Sprague obtained 382 lines of corn that were at various stages of selfing from a private breeder (Milton Robinson?) in southern Iowa. The source population(s) of the lines has not been established and we do not have further information concerning their source. These materials were grown in the nursery in 1952 at Ames, IA.

Inbred B52 was recognized in the S3 generation of selfing as having a vigorous plant with relatively good ear size and good grain. Evidently, its pollen shed at that time was not recognized as a problem. In particular, it was noted for an extremely hard stalk. In its first hybrid performance tests, it was not outstanding but must have been good enough so that it was not discarded. In Russell's 1958 field book, B52 was labeled for discard because of poor topcross (hybrid) performance but this was marked out and it was designated B52. Fortunately, in the same summer, the line was included in a test at Ankeny, IA (USDA Corn Insects Laboratory) where there was an evaluation for second generation European corn borer. It had the lowest count for stalk and shank cavities, which ranged from 0 to 8.4. Artificial infestation, 3 egg masses per plant, had been made during pollen-shedding stage of plant development. Evaluations in following years continued to show this high level of resistance for B52: at infestation levels of 600-700 larvae per plant, B52 has averaged 10-15 inches of stalk tunnelling compared to 30-35 inches for inbreds Mo17 and B73.

B52 has been examined for RFLP patterns with 82 mapped clones. In cluster and principal component analyses of the RFLP data, B52 has been more closely associated with Lancaster inbreds, particularly Oh43 types. RFLP mapping studies have been initiated to identify the B52 chromosome segments contributing to corn borer resistance and to facilitate transfer of these segments into elite inbred backgrounds.

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