Showing papers by "William B. Miller published in 2005"

1-methylcyclopropene (1-MCP) based technologies for storage and shelf-life extension

Abstract: 1-MCP is an inhibitor of ethylene perception that can affect ripening and/or senescence processes in fruit, vegetables and ornamental products. Responses to 1-MCP vary widely, including within a product type, perhaps because of cultivar and/or storage regime differences. In general, however, 1-MCP delays ripening and senescence and reduces ethylene production, respiration, color change and softening. Information about these effects is increasing rapidly and is available on a regularly updated web site (http://www.hort.cornell.edu/mcp/). 1-MCP is registered for use on a number of horticultural products in several countries, although commercial information remains limited except for apple fruit and ornamental products. The commercial potential for 1-MCP will be affected by many factors including the product response (especially in relation to quality as perceived by the consumer), how successfully 1-MCP use can be incorporated into handling, storage and transport systems, the scale of the industry involved, competition in the marketplace, and whether it provides access to markets that are otherwise unavailable using current technologies.

Paclobutrazol and Uniconazole Solutions Maintain Efficacy after Multiple Lily Bulb Dip Events

Abstract: One of the problems associated with preplant bulb dips into plant growth regulator (PGR) solutions is the lack of knowledge of solution effi cacy as an increasing number of bulbs are treated. We evaluated the effectiveness (“longevity”) of paclobutrazol (Bonzi) and uniconazole (Sumagic) solutions repeatedly used to dip hybrid lily (Lilium sp.) bulbs. Experiments were conducted over a 2-year period, using sequential 1-minute dips into paclobutrazol (100 or 200 mg·L–1) or uniconazole (2.5 mg·L–1). No difference in plant height occurred as the number of bulbs dipped into PGR solutions increased to at least 55 bulbs per liter. This was true whether bulbs were washed (with tap water to remove soil particles attached to the bulbs) or unwashed prior to the PGR dip. These fi ndings have an important impact on cost effectiveness of bulb dips, as the more times the solution can be used, the lower the cost. Washed bulbs were taller than unwashed bulbs due to lower PGR liquid uptake in washed bulbs (about 1 mL less per bulb) compared to the unwashed bulbs. These results indicate that the hydration condition of bulbs prior to dipping can affect the amount of PGR liquid uptake and therefore fi nal plant height.

Variation in Fusarium-induced Ethylene Production among Tulip Cultivars

Abstract: Ethylene evolution is a well-known consequence of Fusarium infection of tulip (Tulipa gesneriana) bulbs, yet little is known about the bulb-pathogen interactions involved in the induction or the time course of ethylene production in the infected bulb. Bulbs of 36 tulip cultivars were wounded, inoculated with a liquid Fusarium suspension (isolated from infected bulbs, and grown on agar plates) and held at 21°C. Control bulbs were wounded, but not inoculated. Ethylene production was monitored by headspace accumulation and gas chromatography. The results indicated that ethylene could increase rapidly after a lag phase of at least 8 days after inoculation, but there was a great variability in ethylene production among cultivars. Of the cultivars tested, the highest ethylene producer was ‘Furand’, which evolved more than 340 µl/kg fwt wt/h (ca. 250 µl/bulb/day) on the 12 th day after infection. By 19 days, inoculated ‘Furand’ and ‘Nashville’ produced ethylene at ca. 800 µl/bulb/day. Approximately 40% of the cultivars produced ethylene at rates greater than 150 µl/bulb/day, and only 11% of them produced less than 5 µl/bulb/day. These results suggest high-ethylene producing tulips should be stored separately from other cultivars, or that increased ventilation should be maintained during storage or transportation. Knowledge of cultivar variation might also be useful in breeding programs.

The Development of Upper Leaf Necrosis in Lilium

Abstract: A necrotic disorder occurs on upper leaves of many oriental hybrid lily (Lilium L.) cultivars, including the most-widely-grown ʻStar Gazerʼ. We term this disorder "upper leaf necrosis" (ULN) and hypothesize that it is a calcium (Ca) defi ciency. We demonstrated that Ca concentration in necrosed tissues was nearly six-fold below that of normal leaves (0.10% vs. 0.57% dry weight), and that Ca concentration was negatively associated with percent- age necrosed leaf area. It was concluded that ULN is a Ca defi ciency disorder. When the symptoms were slight, early ULN symptoms appeared as tiny depressed spots on the lower surface of the leaf, or as water-soaked areas when the disorder was severe. Most commonly, ULN began on the leaf margin. The injured areas turned brown, leading to leaf curling, distortion, or tip death. ULN occurred on leaves associated with fl ower buds and leaves immediately below the fl ower buds. For the plants grown from 16-18 cm circumference bulbs, the fi ve leaves directly below the fl ower buds and larger leaves associated with the 1st and the 2nd fl ower buds were most susceptible. In general, fl ower buds were not affected by ULN, and continued to develop and fl ower normally, even though they were associated with subtend- ing, highly distorted leaves. Eighty-fi ve percent of plants began to exhibit ULN symptoms 30-40 days after planting (i.e., 24-34 days after shoot emergence). This was the stage when the 6th or 7th leaf under the bottom fl ower bud was just unfolded. Light was not the main factor that initiated ULN, however, ULN severity was greatly increased by light reduction, as leaf transpiration was reduced.

Post-heat Stress Respiration Pattern of Tulip Bulbs in Storage

Abstract: Dutch-grown tulip bulbs are shipped around the world via ocean freight. Normal transport temperatures are 17 to 20°C, but bulbs can be improperly subjected to high temperature stress due to equipment failure or mishandling. To understand effects of heat stress on internal metabolism of tulip bulbs, we determined the responses to heat treatment of a heat sensitive cultivar (‘Apeldoorn’) and a heat-resistant cultivar (‘Sevilla’). In addition, we tested the hypothesis that heat-induced injuries are related to endogenous ethylene production by treating bulbs with an inhibitor of ethylene perception, 1-methylcyclopropene (1-MCP), prior to heat treatment. Bulbs, either untreated or treated with 1-MCP, were exposed to 35°C for 1 to 7d, and then respirations rates at 17°C were assessed daily. For non-heated bulbs, respiration rates of the heat-resistant cultivar ‘Sevilla’ were much higher than ‘Apeldoorn’. For heated bulbs, respiration rates generally increased as the length of heat stress increased, and patterns of change were similar for both cultivars. Highest rates of respiration over time were found at 2 or 3 days after removal from heat. Effects of 1-MCP were significant, but depended on the stress level.