The physical basis for using the close linkage of the y (white endosperm) and ms (male sterile) genes to eliminate detasseling in the production of hybrid seed depends upon the ability of a seed sorter to separate white from yellow kernels.
About 4.6 lbs of hand-pollinated MA-400 segregating ca. 50% y ms, and about 2.4 lbs of IL-677a segregating ca. 50% y ms, were run by Mr. Al Rodriguez of Geosource in Houston, Texas through their Megasort 6, 7-ring light machine, at the rate of 250 lbs per hour. In each case, the kernels sorted as white (y ms) by the machine still carried 6 to 7% of the most pale yellow kernels. Apparently the machine can be adjusted to remove more of the yellow. It is significant that no white kernels were observed in the yellow and there was a slight deficiency in yellow kernels (46% instead of 50%). Also, if the sorted white kernels were sent through the machine a second time with the kernels in different positions, it would probably remove the balance of the yellow kernels. That is, if the electric eye just sees the white scutellum of a yellow kernel, it may respond as if the kernel were white.
The following data on the efficiency of the Megasort 6 operation were
obtained by hand-picking the white for yellows accepted in error by the
machine:
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| Total machine-sorted as white |
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| Yellows accepted as white |
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| Percent efficiency of machine |
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During the backcrossing of the y ms segment into a given inbred, selection must by practiced to insure good color contrast. For some inbreds with dingy pericarp color (such as C-13) it is difficult to get acceptable contrast.
The y ms system seems ready to be put into use, at least as an alternative means when all sterile cytoplasms fail. In addition to various y ms sweet corn inbreds, B73 and MO-17 have been converted to y ms. They are in the hands of seed producers (Pioneer, Acco & Funks).
Walton C. Galinat
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