A Lagrangian stochastic simulation model for evaluating cross fertilization in maize

The extensive adoption of genetically modified crops has spurred the need to quantify movement of genetic traits in the environment due to pollen flow and cross fertilization. Cross fertilization between varieties of a species results in outcrossing and the subsequently formed hybrids may express traits from either parent (e.g., when yellow seeds occur on normally white-kernel ears of maize). A Lagrangian stochastic (LS) model was developed specifically for maize pollen transport in a maize canopy. It was used to analyze maize outcrossing data in which yellow-seeded (Y) maize and white-seeded (W) maize were planted in spatially separated blocks. Outcrossing percentage was determined by separately counting yellow and white kernels on individual ears in each row of the white-seeded type. Data were obtained from two sources. The first was a newly reported experiment wherein Y and W maize plants were planted alternately in a series of contiguous blocks, each containing a different numbers of rows. The planting arrangement yielded pollen source to receptor plant distances ranging from 1 to 53 m. The second data set was from the classic study of Jones and Brooks (1950), in which blocks of W plants were separated from a large block of Y plants by distances ranging from 1 to 530 m. The LS model predictions of outcrossing were highly correlated with the observations for both of these studies. The model yields a physical basis for interpreting the affects of separation distance and border rows on outcrossing potential and will be useful for analyzing and designing studies of outcrossing in maize and other wind-pollinated plant species.