Irrigation and fertilization modulate guayulin content in guayule (Parthenium argentatum A. Gray) and its hybrids.

The guayulin content of guayule (Parthenium argentatum Gray) is subject to seasonal variation and follows specific patterns that are dependent on the accession and the organ (stems or leaves). However, little is known about guayulin in response to agronomic management such as irrigation or fertilization. A 24-month experiment was performed to investigate the accumulation of guayulin in one guayule accession (R-1040) and two hybrids (CAL-1 and AZ-2), in relation to crop system (irrigated or non-irrigated) and the nitrogen fertilizer units (NFU 0% or 100%). Irrigation increased biomass, which likely diluted guayulin concentration, but contributed to increase guayulins yield in both organs (stems and leaves). Fertilization had no effect on guayulin and resin production, but it increased the number of stems and total biomass. The pattern of accumulation of guayulins between stems and leaves was different. Differences were observed between the hybrids and the pure accession R1040, which was smaller in size but produced more guayulins. A strong relationship was found between guayulin yield and the production of rubber. • Hybrids accessions AZ-2 and CAL-1 behaved differently from pure guayule R1040. • Accession and harvest factors had the most significant effects on guayulin content. • Irrigation and fertilization interaction diluted drastically the concentration of guayulins. • Guayulins C and D seem to play a relevant role in the guayulins accumulation. • Strong correlation exists between guayulins and rubber content. [ABSTRACT FROM AUTHOR]