|Van Fleet, Jennifer|
Submitted to: Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 7/2/2004
Publication Date: 7/20/2004
Citation: Cornish, K., Mcmahan, C.M., Mccoy, R.G., Van Fleet, J.E., Fowler, J.L. 2004. Characterization of guayule latex: variation across lines and plant tissues. Meeting Proceedings.p. 239-254. Interpretive Summary:
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 harvest time, branch age, or differences between lines on latex quality. Latex produced from four subfractions of 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, and included a comparison of harvest time for one line. Analysis of the yield data shows that line AZ-R2 had a higher yield overall than the guayule lines 11605 and Cal-6, and older 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 particle size slightly decreasing as stem size increased in all three lines. In all lines, purified latex showed a low protein content; the roots and stem bases had a relatively lower protein concentration than latex from the stems. Molecular characterization of the latex rubber molecules indicated that polymer from all lines and all parts of the guayule plant was of high molecular weight, of low polydispersity and similarly configured as random coils. Physical testing of films made from the different latex samples, and compared with films made from different samples of Hevea brasiliensis latex, indicated that high quality properties could be achieved from all samples. 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 across the root base, or by digging the entire shrub, which would include latex from the roots and stem bases.