Table 7. Changes in the grain yield and yield components through the dometication from diploid to tetraploid, tetraploid to hexaploid and diploid to hexaploid for wheats.

Grain yield components	Diploid old wheat	Tetraploid old wheat	Hexaploid modern wheat	Diploid to tetraploid	Tetraploid to hexaploid	Diploid to hexaploid
Grain weight/spike (g)	0.17±0.01	0.45±0.03	0.96±0.04	+	+	+
Grain number/spike	13.2±0.8	32.5±2.2	33.8±1.7	+	+	+
1000-grain weight (g)	36±4.1	42.4±3.6	41.7±3.1	+	0	+
Spike number/plant	5.4±0.2	3.2±0.2	1.9±0.2	−	−	−
Grain yield/plant (g)	0.47±0.04	0.96±0.05	1.83±0.08	+	+	+
Population yield (g/m2)	97.5±10.2	235.6±11.8	467.6±12.3	+	+	+

+ represents a significant increase at P<0.01. − represents a significant decrease at P<0.01. 0 represents no change. Data of yield per plant and population yield were similar in 2009 and 2010, and average data are presented in the table.