Table 1.

Population mean values of the traits under control and drought treatments, analysis of variance for the traits under stress and well-watered condition and relative reduction and heritabilities of the traits under drought condition

Trait	Year	Control	Drought	P values (two-way ANOVA)			Relative reduction (%)	Heritability (%)
				Genotype (G)	Treatment (T)	G × T
Number of main stems	2008	4.30	4.13	<0.001	NS	NS	4.03	74.7
	2009	3.46	3.12	<0.001	NS	NS	9.83	59.5
Shoot dry weight (g)	2008	21.03	12.34	<0.001	<0.001	<0.001	41.32	70.1
	2009	17.51	10.36	<0.001	<0.001	<0.001	40.83	61.2
Shoot fresh weight (g)	2008	259.30	102.50	<0.001	<0.001	<0.001	60.47	79.8
	2009	270.11	113.20	<0.001	<0.001	<0.001	58.09	56.5
Plant height (cm)	2008	137.30	98.28	<0.001	<0.001	<0.001	28.42	64.0
	2009	137.93	98.88	<0.001	<0.001	NS	28.31	49.3
Tuber number	2008	7.17	3.21	<0.001	<0.001	0.002	55.23	73.2
	2009	2.60	1.04	0.014	0.003	0.021	60.00	70.6
Tuber weight (g)	2008	33.79	5.53	<0.001	<0.001	<0.001	83.65	69.2
	2009	10.16	1.06	<0.001	<0.001	<0.001	89.57	65.1
δ13C (‰)	2008	−31.61	−30.28	<0.001	<0.001	0.032	4.21	58.2
	2009	−30.48	−29.78	0.034	<0.001	NS	2.29	22.6
RWC (%)	2008	83.95	58.73	0.004	<0.001	NS	30.04	36.8
Root dry weight (g)	2009	1.36	1.07	<0.001	0.012	NS	21.32	41.5
Root length (cm)	2009	30.62	24.84	<0.001	<0.001	0.011	18.88	45.1
Root:shoot ratio	2009	0.07	0.11	<0.001	<0.001	NS	−43.50	42.3
Number of stolons	2009	5.84	4.09	<0.001	<0.001	NS	29.97	52.3
Dry biomass (g)	2009	18.87	11.43	<0.001	<0.001	<0.001	39.43	60.0