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United States Department of Agriculture

Agricultural Research Service

Research Project: Improvement and Utilization of Natural Rubber- and Castor Oil-producing Industrial Crops

Location: Crop Improvement & Utilization Research

Title: Laboratory and field studies of guayule modified to overexpress HMGR

Author
item McMahan, Colleen

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: November 15, 2012
Publication Date: February 5, 2013
Citation: Mcmahan, C.M. 2013. Laboratory and field studies of guayule modified to overexpress HMGR [abstract]. Tire Technology Expo 2013, February 5-7, 2013 Cologne, Germany.

Interpretive Summary: Guayule is under development as a new industrial crop in the US as a source of natural rubber, organic resins, and bioenergy. Genetic modification of guayule for increased rubber yields could significantly contribute to economic sustainability of this new crop. Here we report results from a single gene modification of guayule designed to increased rubber and/or resin production. In the laboratory, increased rubber was found for a modified guayule line; that was not duplicated in the field, probably due to the overwhelming influence of environment in the harsh semi-arid cropland used for cultivation. However, the genetically improved lines had improved survival rates following pollarding (cut at the stem just above the base) harvest. Guayule is often left to re-grow in the field after the initial harvest, then re-harvested. Use of the improved lines might improve productivity in this scenario.

Technical Abstract: We report the genetic modification of guayule to overexpress the isoprenoid pathway enzyme HMGR. The rubber content of two-month old in vitro transformed plantlets showed a 65% increase in rubber over the control for one line (HMGR6), and lower resin for another (HMGR2). In field evaluations HMGR6 was differentiated from control lines in size, biomass, and plant morphology, but not in rubber or resin content. Remarkably, the survival rate following pollarding harvest of modified plants was better than controls, with the highest survival rate for line HMGR6. Results suggest enhanced carbon flux to secondary isoprenoid metabolites such as growth phytohormones.

Last Modified: 9/2/2014
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