Submitted to: Industrial Crops and Products
Publication Type: Peer reviewed journal
Publication Acceptance Date: 12/18/2008
Publication Date: 2/1/2009
Citation: Salvucci, M.E., Coffelt, T.A., Cornish, K. 2009. Improved methods for extraction and quantification of resin and rubber from guayule. Industrial Crops and Products 2009. 30:9-16. Interpretive Summary: The importance of natural rubber for the global economy, concerns about the spread of South American Leaf Blight to Asia, and Type I latex allergy have spurred a renewed interest in developing alternative sources of natural rubber. Guayule, a desert shrub native to the Chihuahuan desert, has long been regarded as a promising alternative to the rubber tree for production of natural rubber. Germplasm enhancement of guayule, whether by traditional breeding and selection or through molecular approaches to trait improvement, requires rapid and reliable methods for determining rubber and resin content in large numbers of plant samples. Unfortunately, existing methods for processing and extracting the plant tissue and for analysis of the extracted material are extremely time-consuming, thus limiting the number of samples that can be screened. To address the need for faster sample throughput, conditions were optimized for automated extraction of dried guayule tissue using accelerated solvent extraction (ASE). In addition, rapid methods were developed for quantification of resin by UV absorption and rubber by evaporative light scattering. Since these methods greatly increase the speed of resin and rubber quantification, they could be used in combination with ASE to increase the throughput of guayule evaluation in germplasm enhancement and agronomic improvement programs.
Technical Abstract: Guayule, a desert shrub native to the Chihuahuan desert, is a natural source of high quality, hypo-allergenic rubber. Unlike rubber trees that produce rubber in lactifers, the rubber in guayule is produced in parenchyma cells of the bark tissue of stems and roots. Consequently, guayule tissue must be mechanically broken before the rubber can be extracted and analyzed. Since rubber extraction and analysis is time-consuming, progress towards increasing the rubber content of guayule through breeding or better cultivation practices has been limited by the slow rate of sample processing. To address the need for faster sample throughput, conditions were optimized for automated extraction of dried guayule tissue using accelerated solvent extraction (ASE) and rapid methods were developed for quantification of resin and rubber. For resin analysis, ultraviolet absorbance was used to determine resin concentration after ASE of the tissue with acetone or acetonitrile. For rubber analysis, evaporative light scattering (ELS) was used to determine the amount of rubber recovered after ASE of the tissue with cyclohexane. Extraction of guayule tissue with high latex content verified that the amounts of resin and rubber determined by these methods were similar to the amounts determined gravimetrically. Since these methods increase the speed of resin and rubber quantification, they could be used in combination with ASE to increase the through-put of guayule evaluation in germplasm enhancement and agronomic improvement programs.