Abstract
Pollen-mediated gene flow (PMGF) is the main mode of transgene flow in flowering plants. The study of pollen and gene flow of transgenic wheat can help to establish the corresponding strategy for preventing transgene escape and contamination between compatible genotypes in wheat. To investigate the pollen dispersal and gene flow frequency in various directions and distances around the pollen source and detect the association between frequency of transgene flow and pollen density from transgenic wheat, a concentric circle design was adopted to conduct a field experiment using transgenic wheat with resistance to wheat yellow mosaic virus (WYMV) as the pollen donor and dwarf male-sterile wheat as the pollen receptor. The results showed that the pollen and gene flow of transgenic wheat varied significantly among the different compass sectors. A higher pollen density and gene flow frequency was observed in the downwind SW and W sectors, with average frequencies of transgene flow of 26.37 and 23.69% respectively. The pollen and gene flow of transgenic wheat declined dramatically with increasing distance from its source. Most of the pollen grains concentrated within 5 m and only a few pollen grains were detected beyond 30 m. The percentage of transgene flow was the highest where adjacent to the pollen source, with an average of 48.24% for all eight compass directions at 0 m distance. Transgene flow was reduced to 50% and 95% between 1.61 to 3.15 m, and 10.71 to 20.93 m, respectively. Our results suggest that climate conditions, especially wind direction, may significantly affect pollen dispersal and gene flow of wheat. The isolation-by-distance model is one of the most effective methods for achieving stringent transgene confinement in wheat. The frequency of transgene flow is directly correlated with the relative density of GM pollen grains in air currents, and pollen competition may be a major factor influencing transgene flow.
Highlights
Crop-to-crop gene flow in agricultural production is a universal occurrence and is a principal factor affecting the varietal purity of cultivated crops [1]
More pollen grains were observed in the SW, W, NW, SE and S sectors that were downstream of the Pollen density in eight compass sectors
The higher seed set and gene flow frequency sectors were detected in the same directions where we found more pollen grains, while the lower seed set and gene flow frequency sectors were detected in the directions with less pollen grain
Summary
Crop-to-crop gene flow in agricultural production is a universal occurrence and is a principal factor affecting the varietal purity of cultivated crops [1]. A field study of transgene flow from GM crop to non-GM crop is an essential first step for a complete evaluation of gene flow and its potential consequences, which will provide a solid base for environmental risk assessment. Previous studies have shown that the pollen flows of different plants differed significantly in their dispersal patterns and that there might be different models for the same plants under various environment and weather conditions [8,9,10,11,12]. In wind-pollinated plants, pollen dispersal can be greatly affected by pollen grain architecture, pollen shape and climatic factors (e.g. weather conditions during blooming period, wind speed and direction, day and night temperature, light and relative air humidity) [13,14]. It is vital to investigate in detail the mode of pollen dissemination for a particular species under field conditions
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