Benefits of Transgenic Insect Resistance in Brassica Hybrids under Selection

Abstract

Field trials of transgenic crops may result in unintentional transgene flow to compatible crop, native, and weedy species. Hybridization outside crop fields may create novel forms with potential negative outcomes for wild and weedy plant populations. We report here the outcome of large outdoor mesocosm studies with canola (Brassica napus), transgenic canola, a sexually compatible weed B. rapa, and their hybrids. Brassica rapa was hybridized with canola and canola carrying a transgene for herbivore resistance (Bt Cry1Ac) and grown in outdoor mesocosms under varying conditions of competition and insect herbivory. Treatment effects differed significantly among genotypes. Hybrids were larger than all other genotypes, and produced more seeds than the B. rapa parent. Under conditions of heavy herbivory, plants carrying the transgenic resistance were larger and produced more seeds than non-transgenic plants. Pollen derived gene flow from transgenic canola to B. rapa varied between years (5%-22%) and was not significantly OPEN ACCESSAgronomy 2015, 5 22 impacted by herbivory. These results confirm that canola-weed hybrids benefit from transgenic resistance and are aggressive competitors with congeneric crops and ruderals. Because some crop and crop-weed hybrids may be competitively superior, escapees may alter the composition and ecological functions of plant communities near transgenic crop fields.

Limited ecological risk of insect-resistance transgene flow from cultivated rice to its wild ancestor based on life-cycle fitness assessment

“…This suggests the efficacy of the transgenes for the increased benefits only under target insect attacks. Our finding of increased fecundity in the hybrids and descendants by the introduction of insect-resistance transgene(s) generally agrees with those in previous studies on the introgression of insect-resistance transgenes from crops to their wild or weedy relatives [2,11,15,18,39,54]. The explanation for the slightly increased seed production by transgenic hybrid descendants in the low-insect field block is possibly the result of a low level of insects occurring under the field conditions, in which some plants were still affected by the remnant target insects.…”

Performance of hybrids between abiotic stress-tolerant transgenic rice and its weedy relatives under water-stressed conditions

“…Even in the absence of exposure to glyphosate herbicide, transgenic hybrids overproducing 5-enolpyruvoylshikimate-3-phosphate synthase (epsps) elevated fecundity and overwintering survival/regeneration abilities than their non-transgenic controls, suggesting that the hybrids can lead to increases in the fitness of weedy populations without herbicide application 43 . The canola-weed hybrids carrying a transgene for herbivore resistance (Bt Cry1Ac) were larger and produced more seeds than non-transgenic plants, which were more remarkable in the presence of a biotic stressor, the diamondback moth 44 . In the present study, application of drought stress induced significant changes in the vegetative and reproductive traits of the transgenic hybrids containing AtCYP78A7 and their parents.…”