Bermuda grass (Cynodon dactylon) is notoriously difficult to control with some commonly used herbicides. We cloned a cytochrome P450 gene from Bermuda grass, named P450-N-Z1, which was found to confer tolerance to multiple herbicides in transgenic Arabidopsis. These herbicides include: (1) acetolactate synthase (ALS) inhibitor herbicides nicosulfuron and penoxsulam; (2) p-hydroxyphenylpyruvate dioxygenase (HPPD)-inhibiting herbicide mesotrione; (3) synthetic auxin herbicide dicamba; (4) photosynthesis inhibitor bentazon. We further generated transgenic soybean plants expressing P450-N-Z1, and found that these transgenic soybean plants gained robust tolerance to nicosulfuron, flazasulfuron, and 2,4-dichlorophenoxyacetic acid (2,4-D) in greenhouse assays. A field trial demonstrated that transgenic soybean is tolerant to flazasulfuron and 2,4-D at 4-fold and 2-fold the recommended rates, respectively. Furthermore, we also demonstrated that flazasulfuron and dicamba are much more rapidly degraded in vivo in the transgenic soybean than in non-transgenic soybean. Therefore, P450-N-Z1 may be utilized for engineering transgenic crops for herbicide tolerance.

Genetically modified (GM) crops tolerant to glyphosate have delivered significant economic benefits in farm management. However, the evolution of glyphosate resistance in weeds due to prolonged intensive use of glyphosate poses a serious threat to this weed management system. It is highly desirable in China to deploy dual herbicide-tolerant corn at the very beginning of GM corn release to delay the development of weed resistance to herbicides. Here, we report the creation and characterization of a herbicide-tolerant corn event SCB-29 that expresses both cp4 epsps and bar genes. This transgenic maize is tolerant to glyphosate up to 3600 g a.e. ha⁻¹ and glufosinate up to 3600 g a.i. ha⁻¹, which are quadruple the recommended rates for the two herbicides, respectively. SCB-29 is an event with only a single copy of T-DNA inserted into chromosome 10 of the maize genome. An event-specific PCR detection method was established and three generations of SCB-29 were detected by event-specific PCR suggesting that the transgenes are stably integrated into the maize genome. Analysis of the expression levels of the transgenes among plants of multiple generations by enzyme-linked immunosorbent assays suggested that the expressions are stable over different generations. Moreover, the major agronomic performances of SCB-29 appear to be similar to those of non-transgenic maize, suggesting that SCB-29 is not likely to have yield drag. Therefore, SCB-29 is an excellent herbicide-tolerant candidate to be developed into a commercial herbicide tolerance transgenic event.

ZDAX5 is a variety of herbicide-tolerant maize that contains the modified P450-N-Z1 gene isolated from Cynodon dactylon (L.) Pers. and the cp4 epsps gene isolated from the Agrobacterium tumefaciens strain CP4 and exhibits high tolerances to flazasulfuron and glyphosate under field conditions. Once ZDAX5 corn is available on the market, the evolution of herbicide-resistant weeds will be delayed by applying glyphosate and flazasulfuron to corn fields. Prior to commercialization, it is critical to assess the safety of ZDAX5 maize. Compositional analysis and feed consumption studies in rodents are an important consideration in the safety assessment of genetically modified crops. The nutritional components of ZDAX5 were analyzed and compared with those of its non-transgenic counterpart. The data showed that all the analyzed components in the herbicide-tolerant maize plants were substantially equivalent to those of its non-transgenic counterpart. Furthermore, most of the measured values from ZDAX5 were within the range of values reported for other commercial maize varieties. The sub-chronic feeding trial was carried out with grains from GM, and non-GM maize were independently added into rodent diets at concentrations of 12.5%, 25% and 50%. As a control, another set of rats was fed with a marketed diet. At the end of the 90-day feeding study, no negative effects associated with the consumption of GM maize were found. These results indicate that the herbicide-tolerant maize ZDAX5 is as nutritious and safe as non-transgenic maize.

Genetically modified (GM) crops expressing insecticidal and herbicide-tolerant traits provide a new approach to agriculture production, but concerns about food safety were often raised by the public. The present research shows the findings of the nutritional assessment of ZDAB3 expressing insecticidal Cry proteins (Cry1Ab and Cry2Ab) and EPSPS protein (G10evo-EPSPS). The key nutrients and anti-nutrients of ZDAB3 maize were examined and contrasted with those of its non-transgenic control maize grown at the same locations during three planting seasons. The values for proximates, amino acids, fatty acids, minerals, vitamins, phytic acid, and trypsin inhibitor assessed for ZDAB3 were comparable to those of its non-transgenic control maize or within the range of values reported for other commercial lines. In addition, no adverse effects related to the G10evo-EPSPS protein in mammals were observed. These data indicated that the expression of Cry1Ab, Cry2Ab, and G10evo-EPSPS proteins in ZDAB3 maize does not affect the nutritional compositions, and ZDAB3 maize is equivalent to non-transgenic maize regarding those important compositions.