|Van Fleet, Jennifer|
Submitted to: Latex International Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 7/30/2004
Publication Date: 8/1/2004
Citation: Cornish, K., Mcmahan, C.M., Mccoy, R.G., Van Fleet, J.E., Fowler, J.L. Characterization of guayule latex: variation across lines and plant tissues. Latex International Conference Proceedings. p. 239-254. 2004 Interpretive Summary: Development of domestic natural rubber-producing industrial crops through biotechnology is funded by the USDA's Agricultural Research Service. Our overall goal is to develop commercially-viable natural rubber-producing crops suitable for cultivation in the temperate climate of the United States. Successful accomplishment of this goal will reduce US dependence upon natural rubber imports, minimize reliance on tenuous supplies of this essential and strategic raw material from developing countries, solve life-threatening Type I latex allergies to protein contaminants in rubber products, and address the need for higher-performing rubber products than currently available in a wide range of commercial and strategic applications. Guayule (Parthenium argentatum Gray), a desert shrub native to the southwestern United States and northwestern Mexico, is under commercial development as a source of hypoallergenic latex, especially for medical applications. Commercial acceptability requires consistently high yield of good quality latex. The results of this study suggest that guayule latex is uniform and of good quality among lines and throughout the plant. Some advantages were found for guayule variety AZ-R2 with respect to overall yield. Latex quality indicators showed low variation with respect to particle size, protein level, and molecular weight. Also, latex quality did not significantly vary between plant tissues. It can be concluded that high quality latex can be obtained whether the plant is harvested by pollarding or by digging the entire plant before processing.
Technical Abstract: Guayule (Parthenium argentatum Gray), a desert shrub native to the southwestern United States and northwestern Mexico, is under commercial development as a source of hypoallergenic latex, especially for medical applications. Commercial acceptability requires consistently high yield of good quality latex. However, little information exists about the effects of different lines or branch age on latex quality. Latex from five year-old guayule plants of three lines from New Mexico were quantified, purified, and characterized including small, medium and large branches as well as a root and stem base fraction. Analysis of the yield data shows that line AZ-R2 had a higher yield overall than the guayule lines 11605 and Cal-6, and mature tissues had more latex than the youngest ones. The youngest stems had similar latex content among the lines, and the overall yield difference was attributable to differences among the larger branches. Rubber particle size distribution, protein concentration, and polymer molecular size/weight were quantified across the experimental design. The rubber particle size was similar among lines, but was age dependent with average particle size slightly decreasing as stem size increased in all three lines. In all lines, purified latex had low protein content. Polymer from all lines and all parts of the guayule plant was of high molecular weight, low polydispersity and similarly configured as random coils. Films made from the guayule and Hevea brasiliensis latex, indicated that high quality properties could be achieved from latex from either source. This study suggests that guayule latex is quite uniform among lines and throughout the healthy plant. Further, high quality latex should be obtainable whether the shrub is harvested by pollarding, cutting above the root base, or by digging the entire shrub, including latex from the roots and stem bases.