Progress report on tests to establish lines homozygous for "inactivated" Ms* alleles

Plants from selfs of plants whose progeny did not segregate male sterile but when crossed on male steriles produced some male sterile offspring should include some that are homozygous for the "inactivated" Ms* locus.

For male sterile-1, there are two lines which give male and female transmission. Plants from selfing the heterozygote were tested on ms ms. For one line, 27 had only fertile progeny, 31 had fertile and male-sterile progeny. For another line, there were 24 and 3, respectively. None of the plants had only male sterile progeny in the test on male sterile-1.

Two lines for "inactivated" Ms2 have been established which show both male and female transmission. For the tests of line 6 on ms2 ms2, there was one plant that produced only fertile progeny and six that had fertiles and male steriles. For line 7, the numbers were 16 and 29, respectively. These numbers suggest a 1:2 ratio, but there was no plant homozygous for the "inactivated" locus. The number of plants tested for line 7 are seemingly adequate for an expectation of one or more homozygotes.

For Ms8, lines were established from two male sterile plants that appeared in F1 from x-rayed pollen applied on ms8 ms8 plants. The male steriles were crossed with a normal inbred and the progeny were selfed. All the selfs segregated for male-sterility, 20 from one line and 12 from the other.

For ms10, lines were established from four male sterile plants that appeared in F1 from ms10 ms10 plants crossed with x-rayed pollen. Again, all the selfs segregated male-steriles, the numbers tested being 22, 3, 21 and 23, respectively, for the four lines.

For golden-1 (g) there was one line from a golden plant crossed with x-rayed pollen. The 13 selfs of plants from the cross with normal all segregated golden.

For the two ms8, four ms10, and one g lines, the x-rayed chromosome which allowed expression of the recessive probably was not transmitted through the female. A possible alternative explanation is that the homozygote itself expresses the recessive character. Tests are continuing with the lines carrying the "inactivated" Ms and Ms2 loci.

Charles R. Burnham


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