Managing the postharvest physiology of unrooted cuttings to enhance shipping and postharvest quality.

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Title: Managing the postharvest physiology of unrooted cuttings to enhance shipping and postharvest quality.
Author: Leatherwood, William Roland
Advisors: Sylvia M. Blankenship, Committee Member
Lisa Oehrl Dean, Committee Member
Heike Winter Sederoff, Committee Member
John M. Dole, Committee Chair
Abstract: United States ornamental plant producers imported approximately $61 million worth of unrooted cuttings in 2006. The top three greenhouse production crops geraniums (Pelargonium L'Hér. ex Ait.), poinsettias (Euphorbia pulcherrima Willd. ex Klotzsch) and New Guinea impatiens (Impatiens hawkeri W. Bull) had a wholesale value of $330 million and were produced from approximately 138 million cuttings. Understandably, improving cutting quality by reducing losses induced by ethylene exposure and shipping damage is an area of active research. To investigate possible areas for improvement in cutting production and shipping we studied the use of ethephon, [(2-chloroethyl) phosphonic acid] in stock plant management, 1-methylcyclopropene (1-MCP) use as an ethylene inhibitor of unrooted cuttings, and modified atmosphere (MA) storage of unrooted cuttings. Application of 700 mL • L-1 1-MCP prior to ethylene treatment prevented ethylene damage to Begonia hybrida 'Anita Louise', Portulaca oleracea L. 'Sleeping Beauty' and Lantana camara L. 'Patriot Sunbeam'. Also, 700 mL • L-1 1-MCP application to poinsettia 'Visions of Grandeur', impatiens 'Sonic Red', geranium 'Rocky Mountain White', Pelargonium peltatum (L.) L'Hérit. 'Mandarin', Petunia x hyrbrida 'Suncatcher coral prism' cuttings caused significant ethylene generation. 1-MCP application reduced geranium' Kardino' root numbers and delayed adventitious root formation of Angelonia angustifolia Benth. 'Carita Lavender', Calibrachoa x hybrida Llave & Lex. 'Terra Cotta', I. hawkeri 'Sonic Red', Portulaca oleracea L. 'Fairytales', Sutera cordata Kuntze 'Abunda Blue Improved' and Verbena x hybrida Groenl. & Ruempl. 'Aztec Wild Rose', though 1-MCP rooting effects were overcome by subsequent immediate exposure to ethylene. Ethephon is used to increase stock plant branching and sink tissues abscission. Ethylene evolution from cuttings harvested from recently treated stock plants is suspected to cause leaf abscission of unrooted cuttings during shipping. Impatiens 'Sonic Red' and 'Sonic White' cuttings harvested from stock plants treated with higher ethephon doses resulted in greater ethylene concentrations during storage. Cuttings harvested 24 hours after treatment with 0, 250, 500 or 1000 mg• L-1 ethephon produced 0.07, 1.3, 1.7 or 5.8 mg •L-1 • g-1 (fresh weight) ethylene in the first 24 hours of storage at 20 °C, respectively. Cuttings harvested 24 hours after treatment with 500 mg• L-1 ethephon stored at 10, 15, 20, and 25°C for 24 hours produced 0.37, 0.81, 2.03 and 3.55 mg • L-1 • g-1 (fresh weight) ethylene. Ethephon treatment effects were measurable on harvested cuttings up to 3 weeks post application. Modified atmosphere storage of impatiens 'Sonic Red', geranium 'Kardino' and poinsettia 'Visions of Grandeur' cuttings showed that cuttings held in 1:20 oxygen:carbon dioxide generated higher ethylene concentrations than any other treatment including atmospheric control. Cuttings stored in ratios of 10:10, 10:5, 5:10, 5:5 oxygen to carbon dioxide generated less ethylene compared to atmospheric control. Cuttings stored in 10:5 performed best during propagation, with less leaf yellowing or abscission than any other treatment.
Date: 2008-04-25
Degree: PhD
Discipline: Horticultural Science

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