Linkage relations of Pe*-d

Galinat found that evergreen stalks, one expression of perennialism, is linked with Su on chromosome 4. This finding was verified by an F2 population in a test cross of evergreen stalks with Su Gl3 We planted only seedlings grown from starchy seeds that were also non-glossy. In this population of 64 plants, almost all were either homozygous or heterozygous for evergreen stalks. Only a few plants could be definitely identified as annuals. These data leave no doubt that Pe*-d is located on chromosome 4.

In a backcross population grown in Major Goodman's experimental field in Raleigh, the results were as shown in the following table.

Table.

Though these results are by no means conclusive, they best fit a sequence of Pe*-d Su Gl3 rather than the other two possible sequences. Galinat had similar results in a population of 200 plants from the same test cross. In both his population and ours there was an excess of evergreen stalks. This may involve the gene Ga on chromosome 4 carried by Palomero Toluqueno, one of the parents of the original hybrid.

If the sequence of genes on chromosome 4 is Pe*-d Su Gl3 and the crossing over between Su and Pe*-d is of the order of 36.8 percent as our data suggest, then Pe*-d must be on the long, not the short arm of chromosome 4.

In this connection it may be recalled that the most "potent" of the polygene segments introduced into an inbred strain of corn from four varieties of annual teosinte all showed linkage with Su on chromosome 4 (PCM, 1974). Whether Pe*-d is part of that gene assemblage in Z. diploperennis or only linked with it has not yet been determined. It seems reasonably certain, however, that the annual teosintes have inherited their polygene segments on chromosome 4 from their diploid perennial ancestor.

Paul C. Mangelsdorf and Mary Eubanks Dunn


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