Plants with white pollen were segregating in a 1976 progeny from a self of +/c2 R-r/r-r (background K55 inbred; b pl P-WW); the colorless aleurone class had been planted. Two plants had white pollen and green anthers; the other plants had yellow pollen and green anthers or yellow pollen and red anthers. Pollinations with white pollen failed to yield seed, and only a few tests established the constitutions of some of the other plants with regard to c2 and r-r.
Subsequent genetic analysis has established that a recessive factor (designated whp), in combination with c2, determines white pollen. No effect of whp on aleurone or anther color is evident; other factors of flavonoid biosynthesis have not been implicated by any observations to date, although C2-Idf apparently is equivalent to c2. The genetic data and interpretations are presented in the following.
From the original source, +/c2 R-r/r-r +/whp selfed, in two plantings, the colorless class gave 17 yellow pollen-red anthered:17 yellow-green:4 white-green (expected for 3:3:1 is 16.3:16.3:5.4). A self of one of the 17 yellow-red plants gave 17 yellow-red:8 yellow-green:2 white-green (expected for 12:3:1 from +/c2 r-r/r-r +/whp is 21:5.2:1.7); a self of one of the yellow-green plants gave 19 yellow-green from c2/c2 R-r/r-r +/+). An F2 progeny from a cross of a white pollen plant (c2 r-r whp) by inbred Mo17 (+ r-g +) gave 25 yellow:2 white expected for 15:1 is 25.3:1.7). In an F2 from a cross of a white-green plant (c2 R-r whp) by an unrelated male (+ R-g +), the colored class (3/4) gave 7 yellow-red:4 yellow-green and the colorless class (1/4) gave 7 yellow-red:5 yellow-green with no white pollen plants (1.7 would be expected). In two F2 progenies from crosses of white-green plants (c2 R-r whp) by unrelated males (+ R-r +), the colored aleurone class (3/4) gave 36 yellow-red and the colorless class (1/4) gave 28 yellow-green and 5 white-green (expect 24.8:8.2).
Certain of the progenies are consistent with whp/whp constitution. In an F2 from a cross of a white-green plant (c2 r-r whp) by a yellow-red sibling (+ R-r whp), the colored class (9/16) gave 5 yellow-red; the colorless class (7/16) gave 3 yellow-red and 11 white-green (expect 6:8). In a self from one of the preceding 5 colored-yellow-red, segregating 3 colored:1 colorless, colored seeds gave 22 yellow-red; colorless seeds gave 12 white-green. A self of one of the above 3 colorless-yellow-red gave 10 yellow-red:4 white-green (expect 10.5:3.5 from +/c2 r-r/r-r whp/whp). Thus it is possible, from +/c2 R/R whp/whp sources, to plant pure stands of white-pollen plants from colorless seeds, as in the next-to-last progeny described above.
White pollen is creamy white in bulk when fresh (more striking on a kraft surface than on a white one), turning buff as it dries. Under low power the grains are starch-filled but nearly white. Plants homozygous for whp and heterozygous for c2 have light yellow pollen, consistent with the dosage effects of c2 in other tissues. Neither +/c2 whp/whp nor c2/c2 +/whp plants show pollen segregation, however, so the trait is sporophytic. Numerous pollinations have been attempted with white pollen, but few to no seeds have been obtained; progeny tests are in progress on these exceptions. No flavonols or flavones appear to be present in white pollen, according to preliminary studies by Susan McCormick (Dept. of Botany, University of Texas).
E. H. Coe and Sheila McCormick*
*Present Address: Plant Biol. Lab.
MSU-DOE, East Lansing, Michigan
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