Risk assessment of pollen‐mediated gene flow from Ga1‐m field corn to dent‐sterile Ga1‐s popcorn

Abstract

AbstractThe popcorn industry in the United States is at risk of genetic contamination because it utilizes the gametophyte factor 1 gene (Ga1) as a barrier against pollen‐mediated gene flow (PMGF) from field corn (Zea mays L.). Popcorn with the Ga1‐s allele accepts pollen only from Ga1‐s corn, allowing for field corn and popcorn to be nearby without isolation. Germplasm is being introduced to the United States to increase field corn diversity that unknowingly contains the Ga1‐m allele, which can overcome Ga1‐s selectivity and pollinate popcorn. The risk to the popcorn industry has been underassessed. Experiments were conducted to model the frequency of PMGF from Ga1‐m field corn to Ga1‐s popcorn under field conditions and to evaluate the role of wind speed and direction using a concentric donor–receptor design in 2017 and 2018 in Nebraska, USA. The PMGF to white popcorn was detected using a field corn pollen donor with yellow kernel color (dominate) and further confirmed with a molecular test. Popcorn kernels were harvested from cardinal and ordinal directions from 1 to 70 m. More than 7 million kernels were screened to detect the PMGF. Information‐theoretic criteria were used to select the best‐fit model. The greatest PMGF (1.6– 4.1%) was detected at 1 m and declined with distance. The PMGF was detected at 70 m, the maximum distance tested. Amplification of Ga1 followed by restriction enzyme digest confirmed that yellow kernelled progeny were hybrids from the result of PMGF. This is the first assessment of PMGF from field corn to popcorn, and the results are alarming for the popcorn industry and export market.