Tests for cytoplasmic restoration of nuclear genetic male sterility

F2 progenies from reciprocal crosses between inbred lines have been grown the past two summers to test for male sterility governed by an interaction between nuclear genes and cytoplasm. Such an interaction would be indicated by segregation for male sterility in F2's from all F1's of one cross, but no segregation in F2's from F1's of the reciprocal cross. Examples of this behavior have been reported in flax.

Tests in F2 of diallel crosses within one group of seven inbreds: A251, Oh43, N28, MS1334, K55, Mo17, and C166; one group of six inbreds: A638, A495, A631, A73, A96, and NYN22; and another group of six inbreds: A660, A659, A344, A71-22, A648, and A632 are complete except A495 x A638, A96 x A73, A96 x NYN22, NYN22 x A96, and A659 x A660. Bulk seed of selfed F1 plants from many of the 7-line diallels and all but a few of the other F1's from those and the two 6-line diallels were available from the corn breeding project. A few new F1's were selfed in the Hawaii nursery. All F1's were tested by growing F2's from at least three different F1 plants. It will be evident from the results reported below that this latter procedure is preferable for such tests. One of the three F2's from A344 x A659 segregated 3 normal:1 golden. The other two were all normal. It is being tested against g. One of the three F2's from N28 x 0h43 segregated 3 normal:1 intermediate dwarf. The three F2's from A344 x A660 segregated for pale green seedlings.

One of the three F2's from one cross, A660 x A648, did segregate 3 normal:1 male sterile. All the male sterile plants had short cobs, about two inches long, with silks very little longer than the cobs. The husks on several ears on male sterile plants were opened and pollen was applied. There were no seeds. In no case was there segregation for male sterility in F2's from all F1 plants of a cross. Such an occurrence in one cross but not in its reciprocal would indicate an interaction between cytoplasm and a nuclear gene. As shown in the next note, that result can be explained by either of two hypotheses.

The inbred lines in the above tests are being tested for cytoplasmic restoration of fertility by crossing them as the female parent with heterozygotes for ms; using y ms/Y + or Y ms/Y + stocks. These tests of many of the inbreds will be grown in 1979.

I wish to thank Dr. Jon Geadelmann and Robert Peterson for making seed of the inbreds, many F2's and F1's available for these tests.

Charles R. Burnham

Please Note: Notes submitted to the Maize Genetics Cooperation Newsletter may be cited only with consent of the authors.

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