Table 1.

Mean chiasma frequency for chromosomes 1 and 2 in four S. tuberosum varieties.

Variety	Chiasma frequency	Chromosome 1 (4×/2×)				Chromosome 2 (4×/2×)
		Short	Long	Total	n	Short	Long	Total	n
Cara (4×)	Overall	1.11 (2.2)	1.96 (2.0)	3.07 (2.1)	27	0.48 (2.7)	2.00 (2.1)	2.48 (2.2)	27
	Per bivalent	0.36 (0.7)	0.96 (1.0)	1.32 (0.9)	14	0.10 (0.6)	1.00 (1.0)	1.10 (1.0)	20
	Per multivalent	1.54	2.00	3.54	13	1.29	2.00	3.29	7
	Per chromosome	0.28 (1.1)	0.49 (1.0)	0.77 (1.0)	27	0.12 (1.3)	0.50 (1.0)	0.62 (1.1)	27
Sante (4×)	Overall	0.62 (1.2)	1.97 (2.0)	2.59 (1.8)	71	0.21 (1.2)	1.92 (2.0)	2.13 (1.9)	71
	Per bivalent	0.23 (0.5)	0.99 (1.0)	1.22 (0.8)	59	0.03 (0.1)	1.00 (1.0)	1.03 (0.9)	60
	Per multivalent	1.42	1.91	3.33	12	1.20	1.50	2.70	10
	Per chromosome	0.15 (0.6)	0.49 (1.0)	0.65 (0.9)	71	0.05 (0.6)	0.48 (1.0)	0.53 (0.9)	71
Maris Peer (4×)	Overall	0.94 (1.9)	1.92 (2.0)	2.87 (2.0)	305	0.40 (2.2)	1.93 (2.0)	2.32 (2.0)	305
	Per bivalent	0.32 (0.6)	0.97 (1.0)	1.29 (0.9)	178	0.04 (0.2)	0.97 (1.0)	1.02 (0.9)	208
	Per multivalent	1.35	1.93	3.28	126	1.15	1.98	3.11	90
	Per chromosome	0.24 (1.0)	0.48 (1.0)	0.72 (1.0)	305	0.10 (1.1)	0.48 (1.0)	0.58 (1.0)	305
Scapa (2×)	Overall (per bivalent)	0.50	0.97	1.47	236	0.18	0.97	1.15	236
	Per chromosome	0.25	0.49	0.74	236	0.09	0.49	0.57	236

The mean chiasma frequency is given for each variety on short and long chromosome arms and in total. In the diploid, the overall chiasma frequency is equivalent to the per-bivalent chiasma frequency because each cell has one bivalent. For tetraploid varieties, the overall chiasma frequency includes all pollen mother cells, the frequency per bivalent includes cells with two bivalents for the given chromosome and the frequency per multivalent includes cells with a multivalent for the given chromosome. The chiasma frequency per chromosome is obtained by dividing the overall frequency by four in tetraploids, or by two in the diploid. In brackets is the fold change between the corresponding tetraploid and diploid chiasma frequencies (4×/2×).