Adaptation, Biometric Traits and Performances of Guayule Lines Grown in Two Mediterranean Environments

The perennial shrub guayule ( Parthenium argentatum A. Gray) has gained interest as a potential source of natural and hypoallergenic rubber in Southern Europe. Although, native to northern Mexico, it is suited to semi-arid and Mediterranean environments. A research study was conducted in Sardinia (Italy) to evaluate adaptation and biometric traits of introduced guayule lines and to determine the contents and yields of rubber and resin obtainable from its aboveground biomass. Seedlings of the accessions AZ-1, AZ-2, P803, and 11591 were field transplanted in 2015 at two locations of southern, and northern Sardinia, respectively, differing for annual precipitation. Plant survival rate, height and width, trunk diameter, leaf chlorophyll concentration and photosystem photochemical efficiency were monitored. Shoots were harvested at 30 months after transplanting and were partitioned into twigs and remaining stems and its rubber and resin contents were determined. Location markedly affected plant survival rates and biometric traits. Dry matter yield of aboveground components as well as contents of rubber and resin and plant rubber and resin yields differed significantly among accessions under comparison. We found that AZ1 and 11591 were the most successful accessions at southern Sardinia site, whereas 11591 was the only accession exhibiting a satisfactory plant survival rate in the northern location.