It is possible to determine the degree of out-cross between genotypes, by planting a white-kernel hybrid next to a yellow hybrid (Wicks and Mack, 1996).
Percent out-cross was calculated as the number of yellow kernels divided by the total number of kernels (white+yellow) per ear.
The observed maximum out-cross was over 82% in all years (Table 2).
The level of cross-fertilizations across site-years fluctuated greatly because of the wind directions, but as a rule, the farther away from the yellow Bt pollen source, the lesser was the percent out-cross (Table 3, Fig.
In the white maize rows on the straight north and south sides of the yellow Bt maize field, a considerable amount (7-15%) of out-cross was recorded, mainly within the 7.
The extent of pollen transfer and out-cross fertilization also depended upon the synchronization of pollen shedding of the yellow maize with the silking of the white maize, and the amount of pollen available from the yellow maize.
In this study, the impact of the asynchrony on the level of cross-fertilization should have been the same to or smaller for out-cross between the two populations than within a population as percent cross-fertilization was influenced by the synchronization of pollination of donor pollen with the receptive silking across two populations (Table 1) rather than synchronization within a hybrid.
Because his pedigree lacked the so-pervasive Northern Dancer and Mr Prospector influences, he was a valuable asset to European breeders as an out-cross
, and as he delivered sons and daughters who have made, and are continuing to make, a considerable mark at stud, he leaves a rich legacy to the breed.