Transgene by germplasm interactions can impact transgene evaluation

Transgenes have been successfully commercialized for qualitatively inherited insect and herbicide resistance traits that show similar effects across genetic backgrounds. However, for quantitative traits like yield, genetic background may affect the measured transgene value. In this paper, we evaluated whether different genetic backgrounds impact the estimated value of a transgene for grain yield, plant height, and anthesis-silking interval for maize by developing isogenic pairs of lines with and without a transgene and testing them in hybrid combination with non-transgenic lines from a complementary heterotic group across eleven environments in the United States. Over all hybrid combinations, the transgene increased yield by 0.2 Mg ha(-1). Across multiple non-transgenic lines of the opposing heterotic group, the transgene effect within a line pair ranged from an increase of 0.8 Mg ha(-1) for the NSS4 (non-stiff stalk) and SS7 (stiff stalk) transgenic lines to a reduction of 0.3 Mg ha(-1) for the NSS5 transgenic line when compared to their non-transgenic isoline. Transgenic hybrids were often taller than non-transgenic hybrids (p < 0.05). Anthesis to silking interval was reduced by four growing degree days overall, but no transgene x genotype interaction was detected among line pairs. Our results show the importance of testing transgene efficacy across a large sample of elite hybrid pairs to assess the gene's value. By only testing in a specific hybrid background, as may be done for qualitative traits like insect resistance, transgenes could be erroneously advanced or eliminated.

Automated summary

This paper evaluated the impact of different genetic backgrounds on the estimated value of a transgene for grain yield, plant height, and anthesis-silking interval in maize. Results showed that the transgene increased yield by 0.2 Mg ha(-1), increased plant height, and reduced anthesis-silking interval. However, there was no genotype interaction observed. This highlights the importance of testing transgene efficacy across a large sample of hybrid pairs to accurately assess its value.