Last year, exceptional kernels were reported from crosses that were made with mixtures of white (c2 whp) and yellow pollen. The results of progeny tests, and interpretations, are as follows:
Transmission of white pollen was found in 23 cases; all 23 occurred on C2 r-g y or C2 sh bz wx ear parents, and none on c2 ear parents. On the other hand, 27 cases of "Half-transmission" (in which the endosperm was like the white-pollen parent but the embryo received the sperm from the yellow-pollen parent) were found, of which 13 occurred on the c2 ear parents and 14 on the C2 ear parents. Consequently, transmission does occur at a low rate (0.3%) on silks of C2 ear parents, but not on white-pollen ear parents except by heterofertilization (0.2-0.3%). The reciprocal heterofertilization, in which the embryo would receive from the white-pollen source, has not been tested in this material; appropriate tests are planned. A few apparent mutations of C2 to c2 were found in the screening.
It is tempting to suggest, since white pollen appears to be "helped" occasionally by mixing with yellow pollen and by C2 silks, that cross-feeding or protection of the pollen tubes is occurring.
E. H. Coe
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