Weather Effects on Cross-Pollination in Maize

Control of pollen dispersal is critical for the successful coexistence of genetically modified (GM) maize (Zea mays L.) and conventional maize. The impact of climate on cross-pollination by GM pollen was simulated in two field experiments with a color-recessive white-grain receptor DSP17007 and a color-dominant yellow-grain pollen donor in 2005 and 2006. The day after silk exertion of about 2500 marked single plants was taken as the basis for comparing weather data (maximum and minimum temperatures, relative humidity, wind speed, and average wind direction) with data on the cross-pollination of the white-grain receptor. Scattered significant correlations were found for all weather factors; only the minimum temperature at night had consistent negative correlations with rates of cross-pollination ranging from r = -0.22 to -0.45, indicating that the latter decreased as temperatures at night increased. In previous complementary field and growth chamber experiments, the grain set on one inbred line correlated significantly negatively with temperature up to 24 h before pollination (r = -0.55 to -0.66) because of pollen agglutination. This affects medium-distance pollen dispersals to a greater extent than short-distance ones; thus, cross-pollination with GM maize may be lower when the pollen donor has a proclivity for pollen agglutination at a high minimum temperature at night.