Novel Genetic Variation Through Altered zmm28 Expression Improves Maize Performance Under Abiotic Stress

We previously reported that extended and increased expression of the native maize gene zmm28 in maize resulted in transgenic events with greater grain yields under optimum field environments. Here we report additional positive impacts of altered zmm28 expression on improving yield stability of maize in the presence of the key abiotic stresses of water deficit and low nitrogen (N). Transgenic zmm28 elite hybrids were evaluated with their wild type (WT) comparators in multiple Managed Stress Environments (MSE), where a water deficit stress was imposed at flowering (FS) or during grain fill (GFS), or where N application was restricted (LN). Across 5 years of testing (2014–2018, 1600 comparisons, 80 hybrids, 43 locations), the ZmGos2-zmm28 lead event DP202216 increased yield relative to WT an average of 479 kg ha-1 (6.6%), 345 kg ha-1 (3.4%) and 166 kg ha-1 (2.0%) in FS, GFS and LN environments, respectively. Maximum observed yield response across 6–12 transgenic hybrids in a single location x year combination was 1181 kg ha-1 (13.9%), 860 kg ha-1 (9.4%) and 834 kg ha-1 (7.0%), relative to WT, for FS, GFS and LN, respectively. Another independent event, DP382118, provided similar yield improvements in the same environments, confirming overall confidence in the performance of the construct functional gene. In a separate genetic penetration study in 2018, DP202216 increased yield an average of 487 kg ha-1 (4.4%) over a combined set of GFS and FS locations, where 6 SS Bulk F3 populations were crossed with 6 diverse NSS testers (36 hybrids), confirming consistent positive yield responses across diverse germplasm under water-limited conditions. The improved yield stability of multiple elite ZmGos2-zmm28 transgenic hybrids demonstrated over multiple years of abiotic stress exposure indicates this novel transgenic variation can contribute to the sustainable intensification of maize production that will be required to address global yield gaps.