Table 4.
Best trait-specific indices identified based on the weighted mean/maximum rank sums (WMMRS) and their coefficients of determination (R²; *: p < 0.05; **: p < 0.01; ***: p < 0.001) on the optimum dates.
| R² (within years; rank-based SVI) |
Best date | R² (validation) | RMSE (Validation) | ||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Trait group | Trait | Rank-based best SVI |
Ranking (WMMRS) | 2015 | 2016 | 2017 | 2015 | 2016 | 2017 | PLSR | WMMRS-SVI | NDVI2 | REIP | PLSR | WMMRS-SVI | NDVI2 | REIP | ||||||
| DM (kg DM ha–1) | Total DM at anthesis | R760_R730 | 12 | 0.33 | *** | 0.11 | ** | 0.33 | *** | 06/25 | 05/18 | 07/11 | 778 | 814 | 642 | 0.18 | 0.18 | 0.19 | 2968 | 3726 | 3676 | ||
| Leaves DM at anthesis | EVI | 13 | 0.39 | *** | 0.29 | ** | 0.44 | *** | 06/25 | 06/23 | 07/11 | 153 | 194 | 178 | 0.25 | 0.16 | 0.18 | 849 | 855 | 825 | |||
| Culms DM at anthesis | NWI-5 | 12 | 0.18 | *** | 0.08 | 0.34 | *** | 06/25 | 06/10 | 07/01 | 0.14 | 0.20 | 1774 | 2200 | |||||||||
| Spikes DM at anthesis | NWI-2 | 12 | 0.11 | ** | 0.23 | ** | 0.18 | * | 06/25 | 06/14 | 06/21 | 197 | 163 | 197 | 0.12 | 647 | |||||||
| Total DM at maturity | NWI-5 | 13 | 0.41 | *** | 0.37 | *** | 0.34 | *** | 06/25 | 07/10 | 07/05 | 880 | 739 | 840 | 0.43 | 0.36 | 0.23 | 0.35 | 3262 | 3090 | 4615 | 4380 | |
| Leaves DM at maturity | EVI | 13 | 0.37 | *** | 0.46 | *** | 0.52 | *** | 06/25 | 06/28 | 07/11 | 95 | 103 | 128 | 0.25 | 0.36 | 0.22 | 0.26 | 429 | 412 | 451 | 411 | |
| Culms DM at maturity | R780_R740 | 13 | 0.45 | *** | 0.42 | *** | 0.29 | *** | 06/25 | 06/23 | 05/17 | 310 | 381 | 420 | 0.37 | 0.35 | 0.18 | 0.36 | 1689 | 1934 | 1829 | 1941 | |
| Chaff DM at maturity | NWI-3 | 13 | 0.18 | *** | 0.21 | ** | 0.10 | 07/16 | 07/08 | 06/21 | 213 | 145 | 178 | 0.12 | 522 | ||||||||
| Grain DM at maturity (GY) | NWI-2 | 15 | 0.51 | *** | 0.26 | *** | 0.27 | ** | 06/25 | 06/28 | 06/21 | 0.33 | 0.35 | 0.20 | 0.26 | 1609 | 1891 | 2248 | 2124 | ||||
| N concentration (NC) [%] |
Leaves NC at anthesis | NWI-3 | 12 | 0.09 | ** | 0.10 | 0.17 | * | 06/25 | 04/05 | 06/08 | ||||||||||||
| Culms NC at anthesis | R787_R765 | 19 | 0.07 | * | 0.09 | 0.23 | ** | 04/24 | 06/28 | 06/08 | |||||||||||||
| Spikes NC at anthesis | R787_R765 | 23 | 0.11 | ** | 0.08 | 0.10 | 04/24 | 04/21 | 07/05 | ||||||||||||||
| Leaves NC at maturity | NWI-2 | 17 | 0.32 | *** | 0.42 | *** | 0.21 | ** | 07/07 | 06/14 | 07/05 | 0.13 | 0.24 | 0.13 | 0.09 | 0.48 | 0.23 | 0.26 | 0.25 | ||||
| Culms NC at maturity | DD | 11 | 0.26 | *** | 0.18 | * | 0.22 | ** | 07/07 | 07/19 | 07/05 | 0.09 | 0.10 | ||||||||||
| Chaff NC at maturity | MCARI1 | 12 | 0.10 | ** | 0.26 | ** | 0.27 | ** | 07/07 | 05/18 | 07/11 | ||||||||||||
| Grain NC at maturity (GNC) | R787_R765 | 15 | 0.07 | * | 0.08 | * | 0.08 | 07/07 | 07/10 | 03/31 | |||||||||||||
| Nup (kg N ha–1) | Total Nup at anthesis | R760_R730 | 13 | 0.37 | *** | 0.14 | *** | 0.33 | *** | 06/25 | 05/18 | 07/11 | 0.14 | 0.19 | 0.20 | 66 | 77 | 77 | |||||
| Leaves Nup at anthesis | PRI | 13 | 0.32 | *** | 0.31 | *** | 0.30 | *** | 06/25 | 06/23 | 07/01 | 0.21 | 0.16 | 0.21 | 30 | 37 | 35 | ||||||
| Culms Nup at anthesis | EVI | 12 | 0.19 | *** | 0.09 | 0.16 | * | 06/25 | 06/10 | 07/11 | 0.14 | 31 | |||||||||||
| Spikes Nup at anthesis | NWI-5 | 12 | 0.13 | ** | 0.20 | ** | 0.10 | 06/25 | 06/14 | 05/25 | |||||||||||||
| Total Nup at maturity | R780_R740 | 13 | 0.43 | *** | 0.19 | *** | 0.36 | *** | 06/25 | 07/10 | 07/05 | 0.37 | 0.32 | 0.16 | 0.31 | 27 | 66 | 71 | 66 | ||||
| Leaves Nup at maturity | R787_R765 | 19 | 0.28 | *** | 0.19 | * | 0.14 | * | 07/07 | 04/21 | 05/25 | 0.10 | 5 | ||||||||||
| Culms Nup at maturity | NDRE_770_750 | 13 | 0.13 | *** | 0.23 | ** | 0.38 | *** | 04/24 | 07/08 | 07/05 | 0.17 | 0.17 | 0.17 | 6 | 9 | 9 | ||||||
| Chaff Nup at maturity | DD | 12 | 0.06 | * | 0.19 | ** | 0.26 | ** | 07/16 | 07/10 | 07/11 | ||||||||||||
| Grain Nup at maturity (GNup) | MSR_705_445 | 13 | 0.31 | *** | 0.21 | *** | 0.37 | *** | 06/25 | 06/28 | 06/14 | 0.27 | 0.29 | 0.16 | 0.30 | 33 | 51 | 56 | 52 | ||||
| Straw Nup at maturity | NDRE_770_750 | 15 | 0.17 | *** | 0.23 | *** | 0.37 | *** | 07/16 | 07/10 | 07/05 | 0.17 | 0.11 | 0.11 | 12 | 17 | 17 | ||||||
| derived DM traits |
Spike density | NDVI3 | 11 | 0.16 | *** | 0.05 | * | 0.14 | * | 06/25 | 06/23 | 07/05 | |||||||||||
| Grain number per spike | Maccioni | 14 | 0.04 | 0.06 | * | 0.06 | 07/16 | 06/14 | 04/13 | ||||||||||||||
| Thousand kernel weight [g] | Maccioni | 15 | 0.15 | *** | 0.07 | * | 0.12 | * | 07/16 | 04/05 | 07/11 | ||||||||||||
| DM translocation efficiency | REIP | 12 | 0.03 | 0.19 | *** | 0.17 | * | 07/07 | 07/08 | 03/31 | |||||||||||||
| DM translocation [kg ha–1] | EVI | 11 | 0.08 | * | 0.20 | *** | 0.07 | 04/24 | 07/08 | 04/13 | 0.06 | 1043 | |||||||||||
| Post-anthesis assimilation [kg ha–1] | NWI-5 | 12 | 0.23 | *** | 0.34 | *** | 0.12 | * | 07/07 | 07/10 | 03/31 | 0.19 | 0.17 | 0.14 | 0.15 | 1187 | 1589 | 1963 | 1820 | ||||
| Contribution of post-anthesis assimilation to grain filling |
PSRI | 11 | 0.05 | * | 0.28 | *** | 0.09 | 04/24 | 07/08 | 06/08 | |||||||||||||
| Total N utilization efficiency | NWI-2 | 15 | 0.25 | *** | 0.12 | ** | 0.16 | * | 06/25 | 07/19 | 05/17 | 0.13 | 12.69 | ||||||||||
| Harvest index | R780_R740 | 14 | 0.09 | ** | 0.10 | ** | 0.30 | *** | 07/16 | 07/10 | 07/11 | 0.15 | 0.06 | ||||||||||
| Grain N utilization efficiency | EVI | 12 | 0.21 | *** | 0.14 | *** | 0.21 | ** | 06/25 | 07/19 | 07/05 | ||||||||||||
| derived N traits | Contribution of post-anthesis N uptake to total Nup | EVI | 12 | 0.22 | *** | 0.15 | *** | 0.05 | 06/25 | 07/08 | 07/11 | 0.11 | 0.07 | 0.23 | 0.24 | ||||||||
| N harvest index | RVSI | 14 | 0.22 | *** | 0.14 | *** | 0.28 | ** | 07/07 | 07/08 | 07/11 | ||||||||||||
| Total N translocation [kg ha–1] | MND_750_705 | 13 | 0.42 | *** | 0.11 | ** | 0.21 | ** | 06/25 | 05/18 | 07/11 | 0.18 | 62 | ||||||||||
| Leaves N translocation [kg ha–1] | DD | 12 | 0.42 | *** | 0.30 | *** | 0.26 | ** | 06/25 | 06/23 | 07/11 | 0.12 | 0.25 | 0.17 | 0.21 | 30 | 26 | 34 | 32 | ||||
| Culms N translocation [kg ha–1] | RVSI | 11 | 0.26 | *** | 0.14 | * | 0.08 | 06/25 | 07/19 | 07/01 | |||||||||||||
| Spikes N translocation [kg ha–1] | NDVI4 | 11 | 0.14 | *** | 0.28 | ** | 0.06 | 06/25 | 06/14 | 05/17 | |||||||||||||
| N translocation efficiency | MND_750_705 | 12 | 0.28 | *** | 0.26 | *** | 0.25 | ** | 07/07 | 07/19 | 07/11 | ||||||||||||
| Post-anthesis N uptake [kg ha–1] | DD | 15 | 0.08 | * | 0.14 | *** | 0.10 | 07/16 | 07/08 | 06/08 | |||||||||||||
| other | Flowering (days in June) | MTCI | 13 | 0.32 | *** | 0.54 | *** | 0.63 | *** | 07/16 | 07/08 | 07/05 | 0.27 | 0.26 | 0.15 | 0.24 | 5.8 | 2.8 | 2.4 | 2.4 | |||
See Figure 2 for WMMRS of all index–trait combinations. For WMMRS-based best indices, best measurements dates are reported. Using milk ripeness measurements, WMMRS-indices, NDVI2, REIP, and PLSR were calibrated in each year and validated in each other year, resulting into six validation datasets per trait. Validation R² and RMSE are reported as averaged from these six validation cases if the prediction for at least four validation cases was significant (p < 0.05). Refer to Supplementary Table 2 for individual validation results and to Supplementary Table 3 for calibration results.