Performance of USDA guayule lines in the northern Negev of Israel

The rubber yield of the guayule plant (Tarthenium argentatum) is determined by its rubber concentration and biomass production, both of which are a function of genetic constituents and environmental conditions. With the aim of selecting best performing lines of guayule under the climatic conditions of the northern Negev of Israel, two-yr-old guayule plants from 13 USDA lines were evaluated for height, spread, canopy fresh and dry weight, branch and leaf dry weight, rubber and resin concentration, and rubber and resin yield per plant. Significant differences were found among the lines for all the characteristics tested. Lines 11600 and 11604 excelled in rubber and biomass production and were taller and more uniform than the other lines; whereas line N593, conventionally used as a standard, performed poorly and was less uniform. The correlation between rubber yield per plant and rubber concentration was poor, rubber yield being related mainly to biomass production and to a lesser degree to height and spread of the plants. Taken together with the fact that biomass production was more variable than rubber concentration, this finding suggests that breeding and selection of guayule for high rubber yield should be directed primarily towards improvement of biomass production rather than rubber concentration. In the northern Negev of Israel, USDA lines 11600 and 11604 performed well.