Guayulin content in guayule (Parthenium argentatum Gray) along the growth cycle

Abstract

The commercial development of guayulins might help spur industrial-scale applications of guayule as an alternative source of natural rubber, making necessary to build knowledge on their seasonal response and accumulation in plants. In the present study, the seasonal content of the four known guayulins (A–D) was profiled in 14 different guayule accessions, including hybrids, from age 13 months to age 23 months. Analysis revealed that the accessions could be categorized into four groups based on guayulin content and potentially reflective of their genetic origin and hybridization: one rich in guayulin A, one rich in guayulin C, one rich in guayulin D, and one with intermediate values. Despite the evident differences in guayulin profiles, all four groups shared the same general response. The content of guayulins A and B increased between April and September, followed by a drastic fall in content in November likely triggered by low temperatures, and then a gradual recovery. By contrast, the content of guayulins C and D was much more stable, especially for those accessions showing the highest production. The relationship between the guayulins was useful to characterize their evolution during the growth cycle, with some groups halting production of guayulins during the summer (group rich in guayulin C) and others initiating production earlier, after the winter period (groups rich in guayulin A and those with intermediate values). The higher producers of guayulins were the accessions 11591(CL-1) and AZ-6, and the best harvest time was between September and November, depending on climatic conditions.