Table 1.

Overview of the experimental design: genotypes tested, substrates, nitrogen (N) conditions, and number of plant replicates per sampling date × genotype under each N condition in the three experiments.

Experiment (code–site–year)	Genotype tested	Substrate	Nitrogen condition	Plant replicates per sampling date and genotype	Cumulative N supply		Substrate initial N amount		N available		Nitrogen nutrition index
					g plant−1	kg ha−1	g plant−1	kg ha−1	g plant−1	kg ha−1	BBCH 16–18	BBCH 19	BBCH 30–32	BBCH 59
LR15 Le Rheu 2014-2015	AMBER ASTRID AVISO EXPRESS MOHICAN MONTEGO	Soil-Sand	Low-N High-N	5 5	0.22 1.47	25 165	0.18	21	0.40 1.65	46 186	0.82 0.90 *	– – –	0.63 1.23 ***	– – –
GR15 Grignon 2014-2015	AVISO	Attapulgite clay pebbles	Low-N High-N	6 6	0.26 1.56	29 175	0.25	28	0.51 1.81	57 203	– –	0.79 1.08 ***	0.72 0.96 ***	0.78 1.11 ***
GR18 Grignon 2017-2018	AMBER AVISO EXPRESS MOHICAN OLESKI	Attapulgite clay pebbles	Low-N High-N	7 to 8 6	0.24 1.79	26 200	0.25	28	0.49 2.04	54 228	1.16 1.25 *	0.76 0.84 *	0.81 1.09 ***	0.67 1.03 ***

In GR15 and LR15 experiments, each genotype was grown under the two N conditions, in contrast with GR18, where only AVISO was grown under the high-N condition. The mineral N available in pots for plant growth comes from that initially present in the substrate and that supplied by fertilization. The N Nutrition Index (NNI) was calculated on the genotype AVISO at four growing stages before flowering (BBCH 16–18, 19, 30–32, and 59). The significance codes (

^***P-value < 0.001,

^*P-value < 0.05) refer to a comparison of NNI means carried out by pooling all genotype samples under the same N condition at the same sampling date in order to compare low-N and high-N conditions at four phenological stages (n = 30 for both N conditions in LR15, n = 6 for both N conditions in GR15 and n = 6 and 37 for high and low N-conditions respectively in GR18).