Dormancy of Floral Buds of Rabbiteye Blueberry in a Mild Winter Climate

Schuchovski, Carolina; Biasi, Luiz Antonio

doi:10.1590/1678-4324-2021190755

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Article - Agriculture, Agribusiness and Biotechnology • Braz. arch. biol. technol. 64 • 2021 • https://doi.org/10.1590/1678-4324-2021190755 copy

Dormancy of Floral Buds of Rabbiteye Blueberry in a Mild Winter Climate

Authorship SCIMAGO INSTITUTIONS RANKINGS

HIGHLIGHTS

This work studies the dormancy dynamics of blueberries growing in mild winter regions.

The four rabbiteye blueberry cultivars meet the chilling requirements in the study.

The floral buds of 'Delite' are more precocious than the other cultivars.

Insights on how temperate fruit species could behave in warming climate scenarios.

Abstract

Blueberry is an important fruit crop, with many health benefits. Despite its importance, much remains to be studied concerning the dormancy dynamics in rabbiteye cultivars growing in a mild winter climate. In this research, the dormancy in blueberry, rabbiteye cultivars ‘Bluegem’, ‘Climax’, ‘Delite’, and ‘Powderblue’, was studied in a mild winter region. The single-node cuttings biological test and the evaluation of the hydric status were performed in dormant winter reproductive buds. These experiments were performed during fall and winter in one year (2016). Moreover, chilling hours under or equal to 7.2 ºC were measured, and chill units were calculated according to Utah Model [¹1 Richardson EA, Seeley SD, Walker DR. A model for estimating the completion of rest for "Redhaven" and "Elberta" peach trees. HortScience. 1974;9(4):331-2.], Modified Utah Model [²2 Ebert A, Petri JL, Bender RJ, Braga HJ. First experiences with chill-unit models in Southern Brazil. Acta Hortic. 1986 May;184:79-86.], and Blueberry Model [³3 Spiers JM. Chilling regimens affect bud break in 'Tifblue' rabbiteye blueberry. J Am Soc Hortic Sci. 1976;101(1):88-90.]. In conclusion, the four cultivars showed a similar pattern, revealing a dormant state in the initial sampling dates and a released dormancy in the final treatments, showing the decrease of dormancy in June and July. However, Delite was earlier than the other cultivars. Bluegem and Delite required 134.0 chilling hours, 127.0 chill units (Utah Model), 198.5 chill units (Modified Utah Model), and 971.5 chill units (Blueberry Model) for 50% of their green tip buds reach the opened bud stage. Climax required 44.0, -11.0, 56.5, and 440.5, respectively. And Powderblue required 44.0, 5.5, 77.0, and 725.0 respectively. This study can bring some insights into crop management and production of this important fruit crop, especially in a global climate-changing scenario, related to flowering and dormancy control, as well as helping to select suitable cultivars to a region, concerning chilling requirements.

Keywords:
blueberry; bud; budbreak; chilling; climate change; dormancy; Ericaceae; Vaccinium

GRAPHICAL ABSTRACT

Utah Chill Unit Model			Blueberry Model
Temperature		Chill units	Temperature	Chill units
ºC	ºF		ºC
< 1.4	< 34	0	< 2	0
1.5 to 2.4	35 to 36	0.5	3 to 5	0.5
2.5 to 9.1	37 to 48	1	6 to 15	1
9.2 to 12.4	49 to 54	0.5	15 to 18	0.5
12.5 to 15.9	55 to 60	0	19 to 21	0
16.0 to 18.0	61 to 65	-0.5	22 to 24	-0.5
> 18.0	> 65	-1	> 25	-1

	Chilling Hours (n. hours ( 7.2 ºC)		Chill Units (Utah Model)		Chill Units (Modified Utah Model)		Chill Units (Blueberry Model)
Period	Period	Accum.	Period	Accum.	Period	Accum.	Period	Accum.
April 01(April 25	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0
April 25(May 9	44.0	44.0	32.5	32.5	48.5	48.5	201.5	201.5
May 9(May 23	0.0	44.0	-43.5	-11.0	8.0	56.5	239.0	440.5
May 23(June 6	0.0	44.0	16.5	5.5	20.5	77.0	284.5	725.0
June 6(June 20	90.0	134.0	121.5	127.0	121.5	198.5	246.5	971.5
June 20(July 4	19.0	153.0	86.5	213.5	86.5	285.0	272.0	1243.5
July 4(July 18	33.0	186.0	-46.5	167.0	8.0	293.0	168.0	1411.5
July 18(August 1	26.0	212.0	100.0	267.0	100.0	393.0	265.0	1676.5

Mean time to budburst (MTB) days
Sampling date	Bluegem			Climax			Delite			Powderblue			Mean
April 25	___		A	___		A	32.3		A	___		A	32.3
May 9	30.4	a	B	25.3	ab	B	23.8	b	B	25.9	ab	B	26.4
May 23	17.0	b	C	14.2	bc	C	11.5	c	C	24.9	a	B	16.9
June 6	14.6	a	C	9.0	b	D	10.0	b	CD	11.6	ab	C	11.3
June 20	8.1	c	D	14.3	ab	C	10.3	bc	CD	15.6	a	C	12.1
July 4	3.8	b	E	4.3	b	E	7.5	a	D	4.5	b	D	5.0
July 18	7.6	a	D	8.1	a	D	6.5	a	D	3.7	b	D	6.5
August 1	3.3	a	E	2.5	a	E	3.0	a	E	2.1	a	D	2.8
CV%	8.6
Final budburst rate (FBR) in %
Sampling date	Bluegem			Climax			Delite			Powderblue			Mean
April 25	0.0	b	D	0.0	b	D	57.5	a	CD	0.0	b	D	14.4
May 9	17.5	bc	C	10.0	c	C	55.0	a	D	25.0	b	C	26.9
May 23	26.7	b	C	20.0	b	C	82.5	a	ABC	30.0	b	C	39.8
June 6	67.5	ab	B	22.5	c	BC	90.0	a	AB	65.0	b	B	61.3
June 20	70.0	a	AB	40.0	b	B	80.0	a	ABCD	77.5	a	AB	66.9
July 4	67.5	bc	B	90.0	ab	A	62.5	c	BCD	92.5	a	AB	78.1
July 18	97.5	a	A	92.5	a	A	100.0	a	A	100.0	a	A	97.5
August 1	97.5	a	A	100.0	a	A	100.0	a	A	100.0	a	A	99.4
CV%	10.6

Velocity of budburst (VB) in buds.day^-1
Sampling date	Bluegem			Climax			Delite			Powderblue			Mean
April 25	___		F	___		F	0.18		D	___		F	0.18
May 9	0.06	b	EF	0.04	b	EF	0.25	a	D	0.10	ab	EF	0.11
May 23	0.20	b	E	0.17	b	DE	0.78	a	C	0.13	b	E	0.32
June 6	0.57	b	D	0.34	b	D	1.09	a	C	0.60	b	D	0.65
June 20	1.27	a	C	0.35	c	D	0.92	ab	C	0.69	b	D	0.81
July 4	1.96	b	B	2.56	a	B	1.10	c	C	2.51	ab	C	2.03
July 18	1.35	b	BC	1.65	b	C	1.83	b	B	3.43	a	B	2.06
August 1	4.28	a	A	4.60	a	A	4.51	a	A	4.91	a	A	4.58
CV%	12.14
Vigorous budburst rate (VBR) in %
Sampling date	Bluegem			Climax			Delite			Powderblue			Mean
April 25	0.0	a	B	0.0	a	C	0.0	a	B	0.0	a	B	0.0
May 9	0.0	a	B	0.0	a	C	0.0	a	B	0.0	a	B	0.0
May 23	6.3	b	B	58.3	a	B	0.0	b	B	5.0	b	B	17.4
June 6	9.1	c	B	41.7	ab	B	11.4	bc	B	61.9	a	A	31.0
June 20	71.4	a	A	88.8	a	A	72.9	a	A	100.0	a	A	83.3
July 4	100.0	a	A	100.0	a	A	80.2	a	A	100.0	a	A	95.1
July 18	95.0	a	A	100.0	a	A	100.0	a	A	100.0	a	A	98.8
August 1	89.4	a	A	97.5	a	A	97.5	a	A	100.0	a	A	96.1
CV%	30.0

Relative Water Content (RWC) in %
Sampling date	Bluegem			Climax			Delite			Powderblue			Mean
April 25	58.3	b	CD	62.8	a	B	55.9	bc	D	54.7	c	CD	57.9
May 9	63.9	a	B	63.3	a	B	63.9	a	AB	58.4	b	BC	62.4
May 23	57.4	b	DE	62.1	a	B	60.2	ab	BC	58.3	b	BC	59.5
June 6	54.1	a	EF	57.0	a	CD	53.9	a	D	54.7	a	CD	54.9
June 20	55.9	ab	DE	57.9	a	C	55.9	ab	D	54.1	b	D	55.9
July 4	50.4	b	F	53.9	a	D	40.8	c	E	42.1	c	E	46.8
July 18	61.9	a	BC	58.1	b	C	57.2	b	CD	59.4	ab	B	59.2
August 1	68.3	a	A	67.9	a	A	65.4	a	A	67.3	a	A	67.2
CV%	2.70
Water Content (WC) in g water.g^-1 bud dry weight
Sampling date	Bluegem			Climax			Delite			Powderblue			Mean
April 25	1.40	b	C	1.69	a	B	1.27	b	C	1.21	b	C	1.39
May 9	1.78	a	B	1.73	a	B	1.77	a	A	1.40	b	BC	1.67
May 23	1.35	b	C	1.64	a	B	1.51	ab	B	1.40	b	BC	1.48
June 6	1.18	a	CD	1.33	a	C	1.17	a	C	1.21	a	C	1.22
June 20	1.27	ab	C	1.38	a	C	1.27	ab	C	1.18	b	C	1.27
July 4	1.03	a	D	1.17	a	C	0.69	b	D	0.73	b	D	0.90
July 18	1.63	a	B	1.38	b	C	1.34	b	BC	1.46	ab	B	1.45
August 1	2.16	a	A	2.12	a	A	1.89	b	A	2.06	ab	A	2.06
CV%	6.30

Cultivars	Sampling date when 50% of GT buds reach OB stage	Chilling Hours (n. hours ( 7.2 ºC)	Chill Units (Utah Model)	Chill Units (Modified Utah Model)	Chill Units (Blueberry Model)	Literature
Bluegem	June 20	134.0	127.0	198.5	971.5	400 [²⁴24 Retamales JB, Hancock JF. Blueberries. Oxfordshire: CABI; 2012. 336 p.]
Climax	May 23	44.0	-11.0	56.5	440.5	400 [²⁴24 Retamales JB, Hancock JF. Blueberries. Oxfordshire: CABI; 2012. 336 p.]
Delite	June 20	134.0	127.0	198.5	971.5	500 [²⁴24 Retamales JB, Hancock JF. Blueberries. Oxfordshire: CABI; 2012. 336 p.]
Powderblue	June 6	44.0	5.5	77.0	725.0	550-600 [³³33 Oliveira PB, Pinto RM, Mota M, Oliveira CM. Chilling effect on three highbush blueberry cultivars. Acta Hortic. 2017 Nov;1180:511-6.]

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