Maize Pollen Longevity and Distance Isolation Requirements for Effective Pollen Control

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Abstract
Pollen is an important vector of gene flow in maize (Zea mays L.). Experiments were conducted to investigate the duration of pollen viability and the effectiveness of isolation distance for controlling gene flow. Pollen longevity was tested by collecting pollen at dehiscence and exposing it in a thin layer in the open air and sunshine for prescribed time periods before assessing pollen viability by measuring seed set after pollination and scoring visual appearance. Isolation distance efficacy was evaluated by growing 12.8‐m2 plot of maize at various distances from a 4000‐m2 pollen source. The pollinator contained either a genetic leaf or seed marker that allowed pollen flow to be measured. Pollen maintained viability for 1 to 2 h after dehiscence depending on atmospheric water potential. The theoretical, maximum distance viable pollen could move was 32 km, assuming pollen was transported linearly at the maximum average afternoon windspeeds for our location, viability was maintained for 2 h, and pollen settling rate was ignored. Cross pollinations occurred at a maximum distance of 200 m from the source planting, and only a limited number of cross pollinations occurred at the shortest distance (100 m). No cross pollinations occurred at 300 m from the source planting. The results are consistent with conclusions that maize pollen is desiccation intolerant and has a high settling rate. The results indicate isolation distance can be a useful tool for controlling gene flow via pollination in research scale plantings.