Assessment of interspecies and intergeneric gene flow for the GM Jatropha curcas event X8#34 with high oleic acid content in seed

GM Jatropha X8#34 was placed for transgene flow assessment in the open field trial on Semakau Island, Singapore, between 2015 and 2017 to evaluate the potential gene flow to its non-GM counterparts and related species. The trial featured the GM Jatropha event X8#34, which is characterized by high oleic acid content, marker-free, and a homozygous transgene. The study focused on cross-pollination from the GM event to non-GM plants, analyzing factors such as distance, wind and insects mediated transfer, using event-specific multiplex PCR analysis of F1 seeds. Pollen dispersal by wind was also assessed to understand the extent of distance traveled and pollen load. Our results showed the maximum observed transgene flow was 4.5%, occurring in non-GM plants located 2 meters in third quarter of 2016, average for four quarters is 2.57%. However, as the distance increased, the transgene flow decreased significantly, at 4 meters distance observed 0.8% in fourth quarter and an average 0.25%. Transgene flow was not observed beyond 4 meters. These results are consistent with the exponential decrease in Jatropha pollen dispersed and captured by traps over distance, with no pollen detected beyond 6 meters through wind dispersal. Furthermore, no intrageneric transgene flow was detected from GM Jatropha to Jatropha integerrima, nor intergeneric transgene flow to related weedy species such as Euphorbia hirta, Phyllanthus niruri, or Ricinus communis (Castor bean), under open-field conditions (2015–2017). The findings suggest that Jatropha pollination is primarily facilitated by short-distance foraging insects, or overlapping branches between adjacent trees enhances cross-pollination rate due to denser floral display, and attracts more pollinators. An adequate separation distance (>8 meters) is sufficient to prevent unintended transgene flow from GM Jatropha to non-GM Jatropha in Singapore ecological conditions. Additionally, transgene flow between GM Jatropha and related horticultural shrub (Jatropha integerrima) or intergeneric relatives like E. hirta, P. niruri, and castor bean is unlikely under open field conditions.