Printed by BCU. Bcu.vetmed.wsu.edu

Calcium deficiencies contribute to thedevelopment of certain fruit disorders in apples,such as bitter pit. Bitter pit has long beenassociated with low levels of fruit calcium(Ferguson and Watkins, 1989)

Bitter pit (BP) is a physiological disorder ofapple fruit that has caused serious losses inHoneycrisp apples for many years

The susceptibility of ‘Honeycrisp’ to bitter pitreduces the amount of fruit pack-out and limitsthe profitability for growers

BP symptoms: necrotic spots on the superficialskin of the fruit. Pits may be few in number tonumerous, they are more prevalent on the calyxend of the fruit. This disorder can be evident atharvest but can develop in storage, resulting inextensive fruit loss (Fig.1)

Background

PRE-HARVEST SPRAY TREATMENTS

Goals and expected results

Washington State University, Pullman, WA, USA; corina.serban@wsu.edu

Corina Serban and Lee Kalcsits

Minimizing Bitter Pit in ‘Honeycrisp’ Apples

Implications

The main advantages to grow ‘Honeycrisp’ applesare:

‘Honeycrisp’ is sold-out from every nursery

Brings good returns on investment

Is being used as a parent in every apple breedingprogram

Market performance/popularity in the market(Fig.9)

This research will benefit the tree fruit industryto minimize bitter pit in ‘Honeycrisp’ apples, aphysiological disorder that leads to significant fruitlosses and is related to calcium uptake anddistribution within the tree

Objectives

References

1. Evaluate how plant growth regulators (PGRs) sprays like gibberellic acid (GA) and Prohexadione-Ca (Apogee®) can enhance or reduce the incidence of BP in ‘Honeycrisp’

GA promotes shoot growth

BP has long been associated with low levels offruit calcium (Ferguson and Watkins, 1989).However, it has been clear that low Ca by itselfis not the only factor in the development of thedisorder. Work by de Freitas et. al (2008) andSaure (2001) suggested that the plant hormonegibberellic acid (GA) might play a role in boththe development of bitter pit and in thetransport of Ca to the fruit

Apogee is a PGR for vigor control in appleswhich will reduce the length of shoot growth

2. Evaluate Control Atmosphere (CA) durationimpacts on BP development, with or without theapplication of 1-MCP to slow fruit ripening

Compare how 1-MCP and rapid CAestablishment during temperature conditioningimpact BP and fruit quality

BP vs. Blotch pit – determine if blotch pit isrelated to 1-MCP treatment or is just a severform of BP (Fig.2)

3. Evaluate how the computer tomography (CT)-imaging helps to quantify bitter pit developmentinternally

Ferguson. I.B. and C.B. Watkins (1989) Bitter pitin apple fruit. Horticultural Reviews. 11:289-355

De Freitas, S. T., C.V.T. do amarante, J.M.Labavitch, and E.J. Mitcham (2010) Cellularapproach to understanding bitter pit developmentin apple fruit. Postharvest Biol. Technol. 57:6-13

Saure M.C. (2001) Blossom-end rot of tomato(Lycopersicon esculentum Mill.)—a calcium- or astress-related disorder? Scientia Hort. 90:193–208

Hewitt, E.W. (1984) Bitter pit reduction in‘Cox’s Orange Pippin’ apples by controlled andmodified atmosphere storage. Scientia Hort.23:59-66

Acknowledgements

Committee members:

Ines Hanrahan, WTFRC

James Mattheis, USDA-ARS

Sara Serra, WSU-TFREC

Kalcsits Lab., TFREC, Wenatchee

WTFRC Funding

Oneonta Starr Ranch

Material and Methods

Fig. 1. BP symptoms in ‘Honeycrisp’ apples two weeks beforeharvest (A) and at harvest (B), Photo credit: Ines Hanrahan

A B

Fig. 2. Severe form of BP (Blotch pit) after 1-MCP treatment. Photo credit:

Ines Hanrahan

Fig.3. CT imaging of mild BP apple (A) and severe

bitter pit apple (B). Photo credit: Dr. Sankaran

Fig. 9. Good quality ‘Honeycrisp’ apples in the supermarket,Yakima, WA, 2015. Photo credit: Corina Serban (WTFRC)

GA and Apogee will be applied in two concentrations(low vs. high)Two times during the growing season: (1) around thetime of petal fall in May (Fig. 4.) and at thinning time (June15)

Fig.4.’Honeycrisp’ floweraround the time of petalfall

Data collectionPre-harvest:Initial flower cluster countHand thinning (mid June)Shoot length (measured every week after the spraytreatments)Return bloom count (subsequent spring count initialflower cluster count)Nutrient analyses for leaves and fruitlets, in June(traditional vs. X-Ray Fluorescence (XRF)), (Fig.5)

Fig.5. X-Ray Fluorescence (XRF),non-destructive way to measure Ca,K and Mg. Kalcsits lab., Wenatchee

POST-HARVEST TREATMENTS

Fruit analysesAt harvest:Maturity analyses (starch index, firmness, soluble solidscontent, titratable acidity, weight, color, internal ethylenecontent, dry matter)CT scans (Fig.6.)Nutrient analyses for fruit (traditional vs. X-RayFluorescence (XRF)), (Fig.5.)Storage:Evaluate treatments after 2 months (November) and 4months (January)

Research will focus on understanding the physiologicalmechanisms of calcium uptake and distribution in apple

Develop pre- and post-harvest management practices toreduce possible financial losses due to bitter pit in‘Honeycrisp’ apples

Apogee spray will inhibit the shoot growth and thereforewill be expected a reduction in BP compared with GAtreatment, used as a negative control (will increase the BPincidence)

Produce bitter-pit free apples at harvest, in order toenhance storability (Fig.8)

months after harvest

1 2 3 4

bitte

r pit %

0

20

40

60

80

100

CA

RCA

Air

CA

RCA

Air

Control

1-MCP

A B

GA APOGEE

LOW HIGH LOW HIGH

UNSPRAYED (CONTROL)

CA Rapid CA RA

1-MCP CONTROL 1-MCP CONTROL 1-MCP CONTROL

After harvest, fruit will be treated or not with 1-MCP at 50ºFCA (2 % O2, 0.5 % CO2) will be establish the day after receipt, and fruit will remain in CA for 1, 2, 4 or 8 weeks followed by storage in air up to 4 monthsFinal storage temperature will be 37ºF

Fig. 6. CT imaging of ‘Honeycrisp’ apples (A) at harvest and (B)

at 15-63 days in storage Photo credit:

Dr. Sankaran

A B

Fig.7. ‘Honeycrisp’ BP incidence following up to 4 month cold storage. BP development was assessed using the same fruit throughout the 4 month storage period. The final assesment was 7 days after fruit were removed from cold storage (Mattheis, 2013 unpublished)

Fig. 8. Bitter pit free apples at harvest, Gleed WA, 2014 Photo credit:Corina Serban (WTFRC)

Controlled atmosphere (CA) storage has long beenknown to reduce bitter pit development (Hewett, E.W.,1984). Previous studies indicated 1-MCP + CA storage for1 week or more reduces BP development compared tountreated fruit stored in air (regular atmosphere) (Fig.7)

The combination of temperature management to reduceBP while use of CA and/or 1-MCP to slow fruit ripeningwill result in reduced disorder development while slowingripening to maintain market quality over long term storageperiods

The goal of the post-harvest component is toidentify CA storage conditions and optimize therapid CA protocol for ‘Honeycrisp’ and determinethe BP development in different storage conditions

A B

Corina Serban