Crop-specific GMO matrix-multiplex PCR: A cost-efficient screening strategy for genetically modified maize and cotton events approved globally

Crop-specific GMO matrices of 199 genetically modified (GM) events, comprising 143 GM maize events with 75 genetic elements and 56 cotton events with 45 genetic elements, were developed to screen globally approved GM maize and cotton events. As per the compiled information in the matrix, frequently present genetic elements were identified using GMOSeek algorithm: eight genetic elements ([P-35S] [r-act] [T-35S] [T-nos] [pinII] [pat] [aad-1] [cp4 epsps]) in maize and four ([P-35S] [T-nos] [pat] [nptII]) in cotton. Based on the cost-efficiency, feasibility of plexing and coverage of GM events, maize-specific tetraplex PCR, targeting Cauliflower Mosaic Virus 35S promoter (P-35S), Agrobacterium tumefaciens nos terminator (T-nos), Cauliflower Mosaic Virus 35S terminator (T-35S) and endogenous alcohol dehydrogenase (Adh1) gene, with limit of detection (LOD) up to 0.5% was developed. For screening of GM cotton events, pentaplex PCR, targeting P-35S, T-nos, neomycin phosphotransferase II (nptII), phosphinothricin acetyltransferase (pat) and endogenous stearoyl-ACP desaturase (Sad1) gene, with LOD up to 0.25% was developed. Practical applicability of multiplex PCR assays was confirmed with six maize samples of proficiency testing and eight spiked cotton samples. The reported tetraplex and pentaplex PCR assays could efficiently screen 94% of maize and 93% of cotton events approved globally. The developed GMO matrices in combination with multiplex PCR could facilitate checking the GM status of seed samples or food and feed products, and monitoring for presence of authorized GMOs in food and supply chain. This approach can be easily employed by low resource GM testing laboratories in the developing countries, as the multiplex PCR assays are easy to operate with less time and cost inputs. The GMO matrices being presented herein are based on the current information of approved GM events of maize and cotton, which can be further upgraded by including new approved GM events. As most of the newly approved GM events are stacked versions of already commercialized GM events, the developed multiplex PCR assays could also be employed to screen for their presence.