The results of meta-analysis for agronomic and phenotypic characteristics for Pilot Phase trials are presented in Fig. 2 (bottom), and the means and standard errors from individual analyses are presented in Table 2. For comparisons between the three GM maize hybrids and the conventional control, mean values from up to 23 Pilot Phase studies were considered, depending on the evaluated GM hybrid and the observed agronomic/phenotypic characteristics (Table 2). The results of Pilot Phase studies indicated that the three GM maize hybrids were not statistically different from the control for the majority of characteristics evaluated (seedling vigor, early stand count, days-to-silking, days-to-anthesis, plant height, root lodging, stalk lodging, and final stand count; Fig. 2). Statistically significant differences between MON-89Ø34-3 × MON-88Ø17-3 and MON-89Ø34-3 × MON-ØØ6Ø3-6 GM maize hybrids and the conventional control (p ≤ 0.05) were detected for grain yield (8.0 vs. 6.6 t ha−1 and 7.9 vs. 6.5 t ha−1, respectively) and grain moisture (17.8 % vs. 16.8 % and 15.5 % vs. 13.7 %, respectively). The mean values for grain moisture and grain yield were higher for the GM maize hybrids in all comparisons (Table 2). In the Pilot Phase trials, no differences were detected between MON-ØØ6Ø3-6 and the conventional control for any of the characteristics measured.Table 2Means and standard errors (SE) for phenotypic and agronomic characteristics of MON-89Ø34-3 × MON-88Ø17-3, MON-89Ø34-3 × MON-ØØ6Ø3-6, and MON-ØØ6Ø3-6 GM hybrids and the conventional control for Pilot Phase studies in Mexico during 2009–2013Characteristic (unit)Pilot Phase trialsMON-89Ø34-3 × MON-88Ø17-3MON-89Ø34-3 × MON-ØØ6Ø3-6MON-ØØ6Ø3-6Mean (SE)Mean (SE)Mean (SE)Number of studiesTestControlNumber of studiesTestControlNumber of studiesTestControlSeedling vigor (1 [poor] to 9 [best])104.7 (0.7)4.5 (0.8)66.5 (0.6)5.8 (0.9)104.4 (0.7)4.5 (0.8)Early stand count21474.2 (188.3)474.1 (180.7)14490.5 (239.9)535.2 (268.6)20501.2 (193.3)494.4 (188.7)Days-to-silking2381.0 (2.8)80.4 (3.0)1679.0 (3.9)78.1 (4.1)2280.6 (3.2)80.9 (2.9)Days-to-anthesis2379.3 (2.7)78.7 (2.8)1677.5 (3.6)76.6 (3.9)2278.6 (3.0)79.2 (2.7)Ear heighta (cm)360.0 (9.7)60.1 (9.2)361.5 (9.2)60.1 (9.2)363.7 (14.8)64.4 (13.4)Plant height (cm)21191.8 (8.8)189.6 (8.9)14177.1 (11.8)173.3 (12.3)20190.5 (9.2)189.0 (9.2)Final stand count20472.4 (187.0)461.9 (176.4)13451.7 (249.0)487.0 (273.5)19484.3 (196.4)473.2 (185.5)Root lodging (%)173.5 (1.5)4.6 (2.0)115.3 (3.3)6.0 (3.4)163.8 (1.9)4.5 (2.1)Dropped earsa 73.6 (3.2)3.3 (2.7)311.3 (10.0)7.6 (6.1)72.6 (2.3)3.3 (2.7)Stalk lodging (%)191.8 (0.7)2.2 (0.5)131.3 (0.7)1.5 (0.5)181.5 (0.4)2.1 (0.6)Grain moisture (%)1717.8 (1.2)*16.8 (1.1)1115.5 (1.0)*13.7 (0.7)1617.0 (1.1)16.6 (1.2)Grain yield (t ha−1)178.0 (0.7)*6.6 (0.8)117.9 (0.8)*6.5 (1.1)166.4 (0.7)6.3 (0.8)* Statistically significant at the 5 % level of significance aData on dropped ears and ear height were collected but not included in meta-analysis. Data on dropped ears were not included because of lack of variability; data on ear height were not included because of an insufficient number of studies for inclusion