Effects of the Ethylene Binding Inhibitor 1-methylcyclopropene on Flue-cured Tobacco (Nicotiana tabacum L.).

Abstract

Taylor, Zachary G. Effects of the ethylene binding inhibitor 1-methylcyclopropene on flue-cured tobacco (Nicotiana tabacum L.) (Under the direction of W. D. Smith and L. R. Fisher). Three separate research experiments were conducted from 2005 to 2008 to determine the effects of 1-methylcyclopropene (1-MCP) on flue-cured tobacco. The first experiment evaluated the use of 1-MCP on ripening delay and holding ability in flue-cured tobacco. Treatments consisted of 1-MCP at a rate of 0.026 kg ai ha-1 applied at 14 d prior to normal final harvest, 14 and 7 d prior to normal final harvest, 7 d prior to normal final harvest, and 7 and 1 d prior to normal final harvest. To determine holding ability and the effect of ripening delay, treatments included a normal harvest, and delaying harvest 10 and 20 d after normal harvest. Holding ability and ripening delay of flue-cured tobacco was not increased by applications of 1-MCP. Value per hectare, grade index, average price, and yield were not effected by applications of 1-MCP and where reduced when harvest was delayed from the normal. The second experiment determined if applications of 1-MCP could inhibit induced senescence from applications of 2-chloroethylphosphonic acid in flue-cured tobacco. Treatments consisted of applications of 1-MCP at 0.026 kg ai ha-1 and 0.0129 kg ai ha-1 as well as 2-chloroethylphosphonic acid at a rate of 1.68 kg ai ha-1. Applications of 1-MCP were applied at: 14 d prior to normal final harvest, 14 and 7 d prior to normal final harvest, 7 d prior to normal final harvest, and 7 and 1 d prior to normal final harvest. Applications of 2-chloroethylphosphonic acid were utilized to induce senescence at the normal harvest timing for every treatment. Spad value measurements were taken prior to 2-chloroethylphosphonic acid applications (base), then 24, 48, and 72-hours after 2-chloroethylphosphonic acid applications. Spad values were reduced for all chemical treatments when compared to the non-treated check. Applications of 1-MCP made prior to 2-chloroethylphosphonic acid applications, could not bind to ethylene receptors so that chemically induced senescence was inhibited. The final experiment determined the effective concentrations of ethylene and 1-MCP as well as determined if prior applications of 1-MCP could inhibit chemically induced senescence in flue-cured tobacco. Treatments consisted of applications of 1-MCP at 0.0129 kg ai ha-1 applied at: 14 d prior to normal final harvest, 14 and 7 d prior to normal final harvest, 7 d prior to normal final harvest, and 7 and 1 d prior to normal final harvest. Leaves were then sampled prior to 1-MCP application and 30-minutes, 1, 2, 4, and 8-hours after 1-MCP applications. All samples were then analyzed by gas chromatograph to determine the effective concentrations of both ethylene and 1-MCP. All remaining tobacco in the field was then subjected to an application of 2-chloroethylphosphonic acid at a rate of 1.68 kg ai ha-1. Spad value measurements were taken prior to the 2-chloroethylphosphonic acid application (base) then 24, 48, and 72-hours after application. Differences in ethylene concentrations suggest that 1-MCP was bound to the receptor site and by 8-hours, 75-97% of the ethylene concentration had evolved from the leaf tissue. Once 2-chloroethylphosphonic acid had been applied for 48-hours, chlorophyll content in all chemical treatments was significantly reduced from that of the non-treated control. Data suggest that 1-MCP occupied ethylene-binding sites but new sites were regenerated and accepted ethylene in the form of 2-chloroethylphosphonic acid and initiated chemical senescence.