Table 6

Effect of cultivar, cluster thinning, and growing season on yield components of own-rooted grapevines in the Yakima Valley, WA. Note: cluster weight can be calculated by multiplying berries/cluster with berry weight.

	Clusters/shoot (prethinning)					Clusters/shoot (post-thinning)
Treatment	1997	1998	1999	2000	2001	1997	1998	1999	2000	2001
Cultivar
Cabernet Sauvignon	1.4 b^a	2.1 b	1.3 b	1.3 b	1.2 b	1.0 b	1.7 b	0.9 b	0.9 b	0.9 b
Riesling	1.9 a	2.6 a	1.7 a	1.9 a	1.8 a	1.7 a	2.1 a	1.2 a	1.5 a	1.3 a
Chenin blanc	nc^b	1.4 c	0.9 c	0.8 c	0.9 c	nc	1.1 c	0.7 c	0.6 c	0.6 c
Thinning
Early	1.6	2.1	1.4 a	1.4 a	1.4 a	1.2 b	1.4 b	0.7 c	0.9 b	0.9 b
Late	1.6	2.0	1.1 b	1.4 a	1.4 a	1.2 b	1.5 b	0.8 b	1.0 b	0.8 b
Control	1.7	2.0	1.2 ab	1.2 b	1.2 b	1.6 a	2.0 a	1.2 a	1.2 a	1.2 a
Interaction	ns^c	ns	ns	ns	ns	**	ns	ns	*	ns

	Berries/cluster					Berry weight (g)
	1997	1998	1999	2000	2001	1997	1998	1999	2000	2001
^aMeans within columns followed by different letters differ significantly at p < 0.05 by Duncan’s new multiple range test.
^bnc: data not collected.
^cCultivar x thinning interaction; , , **, ns: significant at p < 0.05, 0.01, 0.001, or not significant, respectively.
Cultivar
Cabernet Sauvignon	92 a	92 a	56 b	63	59 c	0.98 b	0.90 c	0.84 c	0.81 c	0.84 b
Riesling	55 b	58 c	51 b	58	74 b	1.25 a	1.12 b	1.03 b	0.96 b	0.93 b
Chenin blanc	nc	82 b	79 a	66	87 a	nc	1.63 a	1.32 a	1.33 a	1.26 a
Thinning
Early	72 b	80 a	63	65 ab	73	1.12	1.22	1.14 a	1.04	1.03
Late	82 a	73 b	64	66 a	74	1.13	1.22	1.03 b	1.03	1.03
Control	68 b	79 a	59	57 b	72	1.10	1.21	1.02 b	1.03	0.97
Interaction	ns	***	ns	ns	*	ns	ns	ns	ns	*