Page 126 - PC2019 Program & Proceedings

PLANT CANADA 2019

S37. Mitigation of fruit drop and prolonging of postharvest shelf life in ‘Honeycrisp’ apples using
hexanal
1
1
DeBrouwer, E.J.* ; J.A. Sullivan ; G. Paliyath ; J. Subramanian 2
1
1 University of Guelph
2 University of Guelph, Vineland
‘Honeycrisp’ apples are in high demand; however, the variety has a serious postharvest disorder known as
bitter pit [BP] that renders apples unmarketable and can cause a yield loss of 50%. One technology to
combat these challenges is hexanal, a natural compound that is currently being used to extend the
postharvest shelf life of many fruits. Hexanal slows cell degradation through inhibition of phospholipase-
D (PLD). PLD is an enzyme that initiates autocatalytic reactions, assisting in the degradation of lipids,
leading to ripening and softening of the cell membrane. Hexanal was sprayed as a preharvest solution,
known as the Enhanced Freshness Formulation [EFF], to ‘Honeycrisp’ apples. Quality characteristics
such as colour, firmness, total soluble solids, titratable acidity, and BP progression were assessed. No
significant differences were seen between treatments in quality characteristics, except for BP progression
where the hexanal treated fruit had 5% decrease in BP compared to the control fruit. In assessing these
components, we hope to increase the longevity, marketability and maintain palatability of ‘Honeycrisp’
apples.

Erika DeBrouwer (edebrouw@uoguelph.ca)

S38. The pollen tube growth model for precision blossom thinning of apples
Sherif, S.; C. Allen; K. Yoder
Virginia Tech

Management of apple crop load by chemical thinning is one of the most critical orchard practices that
significantly affect the annual production and profitability of apple orchards. Although the majority of
apple growers in the eastern USA tend to chemically thin their crop within the first four weeks after petal
fall, crop loads not sufficiently thinned during this period could result in trees being thrown into the
biennial bearing with little or no crop in the ‘off’ year. Thinning at bloom provides many advantages, e.g.
better fruit size and return bloom, and it can be used as a supplemental and/or alternative practice to
standard fruit thinning sprays. The application timing of bloom thinning sprays has been subjective until a
group of researchers at Virginia Tech has developed a model known as “the pollen tube growth model”
(PTGM) to precisely determine the day/time for the first thinning application and subsequent thinning
sprays if required. Over the last 13 years, models have been developed for seven apple cultivars including
Golden Delicious, Gala, Fuji, Cripps Pink, Honeycrisp, Granny Smith, and Red Delicious. A system
whereby commercial apple growers in the eastern USA can now use these models has been created by a
collaborative effort between researchers from Virginia Tech and Cornell universities and is now available
on the Network for Environment and Weather Applications (NEWA) website.

Sherif Sherif (ssherif@vt.edu)

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