Early work by Black et al. (1985) showed that
NIRpoor reproducibility. This work also focused on one
or two individual wavelengths rather than using the
entire NIR spectrum as is done in this work. In a
subsequent study on the use of NIR and chemometric
tools, Kleine and Foster (1990) showed that both the
rubber and resin content could be measured directly
and accurately on dried, finely ground, guayule plants.
This technique has been used to assist with screening
of different lines of guayule grown under different
conditions, or from direct-seeding or transplantation
(Foster et al., 1999, 2002). As with the earlier work
by Black et al. (1985), analysis required a time consuming
grinding process to achieve the homogenous
substrate required for the production of high quality
predictive models. A NIR measurement can be complete
in less than one minute, which is much faster
than a traditional gravimetric method that requires
time-consuming extraction and drying. could be used to measure the rubber and resin
concentration in guayule. However, the sample had
to be slowly and carefully ground to obtain a very
uniform substrate. Non-uniform samples resulted in