Estimating the temperature limitations for growth cessasion and floral initiation in red rasberry (Rubus idaeus L.) and the floral-inducing effect of winter chilling

Figures & data

Figure 1. Effects of temperature on growth of three red raspberry cultivars in naturally decreasing daylengths at Ås, Norway during August and September. Data are the means ± SE of six plants per treatment.

Figure 2. Effects of temperature on profiles of flower development stages of lateral buds along the entire shoot of three red raspberry cultivars after growth for 9 weeks at 12°C and 16°C as shown. The data represent one single plant per treatment. No flower buds were observed at 20°C. Buds at stages ≥ 2 are indicated in yellow.

Table 1. Effects of temperature under naturally decreasing autumn daylength on growth and flowering of three red raspberry cultivars during a 9-week treatment period, followed by cold storage for 7 months and forcing in an open high tunnel in the following spring.

Cultivar	Temperature (°C)	Flowering plants (%)	Days to anthesis^a	Flowers per plant	Flowering nodes (%)	Non-breaking nodes (%)	Flowers per lateral	Lateral length (cm)
‘Glen Ample’	12	100	40.6 d^b	308 d	67.1 bc	25.0 c	16.0 d	39.2 c
	16	100	44.6 c	650 c	70.1 b	28.8 c	25.3 bc	52.0 ab
	20	100	48.0 bc	566 c	31.4 f	65.0 a	31.4 ab	56.6 a
Mean		100	44.4	508	56.2	56.2	24.2	49.3
‘Glen Mor’	12	100	41.0 d	297 d	76.6 ab	22.5 c	17.9 d	38.5 c
	16	100	46.2 bc	744 bc	80.3 a	19.7 c	29.3 ab	52.2 ab
	20	100	47.3 bc	913 a	52.6 cd	46.9 b	34.2 a	44.5 bc
Mean		100	44.6	632	71.1	28.5	26.6	45.1
‘Duo’	12	100	47.3 bc	205 d	49.3 d	48.9 ab	14.5 d	41.0 bc
	16	100	55.4 a	286 d	31.8 ef	65.7 a	19.6 cd	43.8 bc
	20	100	50.0 b	838 ab	42.3 de	57.7 ab	32.6 ab	44.6 bc
Mean		100	51.3	397	40.2	58.1	21.1	43.1
Source of variation
Temperature (A)		-	0.001	<0.001	0.02	0.02	<0.001	0.02
Cultivar (B)		-	<0.001	0.02	<0.001	<0.001	ns	ns
A x B		-	0.04	0.004	<0.001	<0.001	ns	ns

^aDays from 11 May.

^bValues within the same column followed by different letters are significantly different at p ≤ 0.05 by Tukey’s test for the different temperatures and cultivars. The data are the means of five replicates, each with one plant.

ns, not significant