The Control of Inter-pollination between Sweet and Flint Corn

The breeding system of sweet corn, a sugary seeded race of Zea mays L., was studied by randomly planting equal numbers of sweet and flint plants and determining the amount of cross-pollination measured by the contamination on sweet ears. It was found that inter-crossing with flint varied significantly from plant to plant; the out-crossing generally was lower than anticipated. The effects of date of silking and tasselling, and protandry of sweet plants on their out-crossing was demonstrated by using multiple regression analysis. Even so, as prediction was still not satisfactory other factors must have been involved. These variables were all highly correlated. A relation between contamination and temporal isolation was established; this was similar to that for spatial isolation. It was postulated that there may have been genetical control of inter-pollination, as later ears on the same sweet-corn plants were not less contaminated than earlier ones and because out-crossing was generally low throughout the experiment.