TABLE 1.

Expression of varying triploid heterosis for key shoot growth parameters of willow in crossing combinations of diploid Swedish cultivars with autotetraploid genotypes under two field sites.

Geno-types	Year 2020 Location I.				Year 2021 Location II.
	Shoot length (cm)		Growth rate/day (mm)	Stem diameter (mm) in June	Shoot length (cm)		Growth rate/day (mm)
	May 5th	June 11th			April 27th	May 1st
Tordis	27.50 ± 6.05 d	95.33 ± 17.27 c	18.27 ± 3.73 b	4.94 ± 0.94 c	50.67 ± 10.30 Bc	82.60 ± 14.14 b	7.98 ± 2.01 b
TH3/12 MPH%	46.53 ± 3.22 b 42.81	158.80 ± 16.67 a 54.73	30, 34 ± 4.12 a 60.55	9.13 ± 1.37 b 38.98	71.70 ± 9.46 a 49.53	141.59 ± 20.03 a 68.85	17.48 ± 4.04 a 97.18
PP-E 7	37.67 ± 1.51 c	109.93 ± 17.17 c	19.53 ± 4.35 b	8.20 ± 0.30 b	45.23 ± 5.10 C	85.11 ± 9.14 b	9.75 ± 1.56 b
Tordis	27.50 ± 6.05 d	95.33 ± 17.27 c	18.27 ± 3.73 b	4.94 ± 0.94 c	50.67 ± 10.30 Bc	82.60 ± 14.14 b	7.98 ± 2.01 b
TH17/17 MPH%	48.93 ± 1.99 ab 53.64	146.03 ± 7.86 ab 43.76	26, 24 ± 2.51 ab 39.57	9.19 ± 0.63 b 42.34	56.11 ± 5.35 b 11.14	118.31 ± 11.86 a 37.15	15.27 ± 1.95 a 70.71
PP-E 15	36.20 ± 3.72 c	107.83 ± 24.51 bc	19, 33 ± 5.94 b	7.98 ± 0.96 b	50.30 ± 5.50 Bc	89.93 ± 11.85 b	9.91 ± 2.18 b
Inger	49.93 ± 3.10 ab	154.50 ± 15.49 a	28, 23 ± 4.77 a	8.87 ± 0.97 b	67.31 ± 6.55 A	130.56 ± 13.47 a	15.66 ± 2.48 a
TH21/2 MPH%	52.00 ± 5.65 a 18.72	178.33 ± 9.34 a 37.88	33, 59 ± 0.70 a 40.66	11.07 ± 0.55 a 29.71	75.63 ± 8.75 a 34.41	146.63 ± 25.02 a 35.98	17.04 ± 3.84 a 34.12
PP-E 7	37.67 ± 1.51 c	109.93 ± 17.17 c	19, 53 ± 4.35 b	8.20 ± 0.30 b	45.23 ± 5.10 C	85.11 ± 9.14 b	9.75 ± 1.56 b

The midparent heterosis (MPH%) was calculated as heterosis over the midparent (MP%) = [(F1-MP)/MP × 100], where F1 is the numerical value trait measurement in the hybrid and MP values are the mean values of the parents (P1 + P2)/2. Results are mean ± SD. Values denoted with different letters show significant differences at P ≤ 0.05 (Duncan’s or Dunn’s test). Bold values highlight the MPH% and CPH% information.