Table of Contents
Jasso Cantú, D., J.L. Angulo Sánchez, and
R. Rodriguez García. 1996. Identification of guayule regions in
northern Mexico, based on rubber yield and coproducts quality. p. 336-339.
In: J. Janick (ed.), Progress in new crops. ASHS Press, Alexandria, VA.
Identification of Guayule Regions in Northern Mexico, Based on Rubber Yield and Coproducts Quality
Diana Jasso Cantú, José Luis Angulo Sánchez, and
Raúl Rodriguez García
- Collecting Sites and Sampling
- Rubber, Resin, and Biomass Measurements
- Morphologic Characteristics
- Physiologic Characteristics
- Table 1
- Table 2
- Fig. 1
- Fig. 2
- Fig. 3
The development of guayule as a commercial crop has encountered several
problems in México, despite a great amount of research and development
carried out in the 1970s and mid 1980s (Angulo and Lopez 1978; Lopez and
Kuruvadi 1985; Kuruvadi 1985; Lopez and Kuruvadi 1987; Kuruvadi 1988). During
this period, a pilot plant established technical feasibility evaluation for the
rubber recovery process, and a commercial unit for rubber production was
designed (Campos et al. 1978). However, the commercial production units have
not been established up to this moment. Among the problems preventing guayule
commercial development are the lack of raw product and the low international
price of Hevea rubber.
The present guayule areas are based on wild stands, the plants are scarce,
widely distributed, and rubber content is variable, ranging from 5% to over 17%
(Jasso et al. 1993). This fact makes difficult to pinpoint the potential
rubber yields per unit area, hence there is no solid basis to calculate
profitability. Furthermore, fluctuations in the rubber price make cost
estimations uncertain. Previously, we proposed to consider guayule as a source
of more than one product, and to defining new applications in order to improve
commercial exploitation (Angulo and Jasso 1995). In addition, we have
considered that selection and reproduction of high yielding clones is critical
to develop guayule as a commercial crop.
We established a productivity index (PI) in order to identify plants with
outstanding features. This index is used in this work to designate high
yielding areas and plants, within the Mexican guayule region. Iodine value was
determined because the resin might be used for varnish and adhesives (Belmares
et al. 1980; Schloman 1988; Schloman and Wagner 1991; Thames and Wagner 1991).
This parameter reflects the presence of double bonds required for these
applications. Because biomass would be used as a feedstock, bagasse quality
was tested by determining protein content after resin and rubber extraction.
Although some data on the protein content in the guayule bagasse have been
reported (Schloman and Wagner 1991), only one previous work on the resin iodine
value determination was found (Belmares et al. 1980). There are no reports on
the possible correlation between rubber or resin production in guayule and the
iodine value. We suggest that the chemicals possessing double bonds (including
fatty acids, terpenoids, and other chemical species) may be related to rubber
In this study, three zones, in two states, Coahuila and Zacatecas, formerly
identified as high rubber yielding areas (Naqvi and Hanson 1983; Lopez and
Kuruvadi 1985), were revisited, guayule shrubs samples collected, and analyzed.
Biomass, rubber, resin, bagasse, iodine value, and protein were evaluated along
with common morphologic characteristics (Kuruvadi 1985; Lopez and Kuruvadi
1987) such as shrubs height and top spread.
Three sites were selected for plant acquisition: Atenco (site 1), close to
Saltillo, Rocamontes (site 2), Coahuila, and Noria de Guadalupe (site 3) in the
state of Zacatecas (Fig. 1). These sites have been subjected to rubber
yielding studies and the molecular weight characteristics reported. Plant
acquisition was carried out during the first week of Sept. 1991. Twenty-five
plants, between 35 and 75 cm height, were randomly selected from each site.
Measurements of the shrub height and spread were obtained in the field, the
results are presented in Table 1. Afterwards, the plants were cut at ground
level and transported to the laboratory, where the total weight was determined.
The leaves were cut from the shrub and the defoliated plants immersed in liquid
nitrogen and grounded in a Wiley laboratory mill with 2 mm screen.
Part of the grounded material was used for biomass quantification. The tissue
was oven dried at 60°C until constant weight was achieved and total dry
weight calculated (Table 2). Resin and rubber content measurements were
performed on 5 g samples, by soxhlet extraction, using acetone and toluene as
the respective solvents. A resin quality determination was effectuated by
double bonds titration using the Wijs method. This was carried out by
dissolving the resin in chloroform and titrating with iodine-bromine.
After resin and rubber extraction, the protein content was determined in the
bagasse obtaining the nitrogen percent by the Kjeldahl method. The protein
content (%Pr) was calculated using the nitrogen percent (%N2) and the equation
(Dintzis et al. 1988): %Pr = 6.25 (%N2). The results from the
morpho-physiologic characteristics were analyzed using a statistical random
design with three treatments (localities) and 25 replications (plants).
Table 1 shows the results for shrubs height and spread, parameters commonly
used for plant selection. The range for these parameters is different within
sites, but the mean values are very similar. These results reflect the
different plants composition of wild guayule stands and are in agreement with
several other reports.
The results for dry weight, percent rubber and percent resin, iodine value and
protein content in the bagasse are shown in Table 2. The weight difference
between plants growing in the three sites, contrasted strongly with the
similarity observed in the height and spread data. Site 3 (Noria de Guadalupe)
and site 2 (Rocamontes) have a difference of only 5%, but that between site 3
and site 1 (Atenco) is approximately 50%, site 3 having the highest plant
weight. This behavior is due to shrub thickness, the plants from site 3 and
site 2 have thicker stem and branches than those in site 1. Despite height,
spread, and weight differences, rubber content are very similar between sites.
Large differences in iodine value between the sites were found.
A relationship between the resin content and the iodine value was noted (Fig. 2). As resin content increases, iodine value diminishes. The chemicals
constituting the resin are a complex mix (Belmares et al. 1980; Schloman and
Wagner 1991) including terpenoids, fatty acids triglycerides (i.e. linoleic,
linolenic, stearic, and palmitic), very low molecular weight (VLMW) rubber, and
a drying oil, "shellac" type. Several of these chemicals contain double bonds,
for example linoleic and linolenic acids, the terpenoids and the VLMW rubber.
Iodine value is an indicator of the concentration of these compounds, but it
was not possible to differentiate between them with this technique. There was
no correlation between rubber and resin content. However when a ternary
diagram was constructed with the rubber, resin and iodine value (Fig. 3) all
the samples lie within a narrow region. This suggests a relationship between
these three variables and rubber biosynthesis.
In order to consider differences in all the physiologic parameters a global
productivity index (PI) was defined, as PI = [%Rb + (%Rs x I2) + (%Bg x Pr)]W,
where Rb = rubber, Rs = resin, I2 = iodine number, Bg = bagasse, and Pr =
protein content. Resin and the bagasse are multiplied by a "quality factor"
which is the double bonds or protein content, respectively. The results
indicate a productivity index of 12.8 for site 1, 23.3 for site 2, and 29.0 for
Site 3 possessed the highest index based on rubber yielding and resin and
bagasse quality. Differences in the parameters did not follow the same trend
in the three sites. Data in Table 2 indicated that for rubber content site 1
> site 3 > site 2, for iodine value site 3 > site 2 > site 1, and
for resin content site 2 > site 1 > site 3. However, the PI results show
clearly that when all factors are considered the difference in value between
the sites is wide. Site 3 has the highest value due to its higher mean total
weight and iodine value; protein and resin content showed smaller differences
but its contribution was limited. Rubber content was similar, and hence is not
a decisive factor. The rubber molecular weight has been considered as a
quality parameter for the rubber. However, previous studies show that
differences in MW are not significant, for plants reaching this height. We
consider that PI might be a valuable selection index to detect outstanding
shrubs for genetic improvement. Although the numbers allow the identification
of high yielding plants (rubber and coproducts) we do not know the highest or
lowest values that will define, the maximum PI or the acceptability limit for
guayule. The analysis of plants from regions with high and low rubber
production will provide this information. According to these results, shrub
height and spread seem not to be the best parameters for plant selection,
intended for integral commercial use, as the product and coproducts yielding is
very different for similar sized plants.
- Angulo Sánchez, J.L. and D. Jasso de Rodríguez. 1996. An overview
of outstanding species from semi arid lands. p. 176-186. In: L.H. Princen and
C. Rossi (eds.), Proc. Ninth Int. Conference on Jojoba and its uses and of the
Third Int. Conference on New Industrial Crops and Products, Assoc. Adv. Ind.
- Angulo Sánchez, J.L. and E. Campos Lopez. 1978. Geographic influence on
guayule rubber. p. 177-190. In: Guayule: Reencuentro en el desierto. Centro de
Investigación en Química Aplicada. Saltillo, México.
- Belmares Sarabia, H., L.L. Jimenez Valdes, and M. Ortega. 1980. New rubber
peptizers and coating derived from guayule resin (Parthenium argentatum
Gray). Ind. Eng. Chem. Prod. Res. Dev. 19:107-111.
- Campos Lopez, E., E. Neavez Camacho, and R. Maldonado García. 1978.
Guayule: present state of knowledge. p. 375-410. In: Guayule: reencuentro en el
desierto. Centro de Investigación en Química Aplicada. Saltillo,
- Dintzis, F.R., J.F. Cavins, E. Graff, and T. Stahly. 1988. Nitrogen to protein
conversion factors in animal feed and fecal samples. J. Anim. Sci. 66:5-11.
- Jasso de Rodriguez, D., J.L. Angulo Sánchez, F. Ramirez Godina, R.
Morones Reza, and R. Rodriguez García. 1993. J. Am. Oil Chem. Soc.
- Kuruvadi, S. 1985. Evaluation of genetic resources of guayule in Mexico.
- Kuruvadi, S. 1988. Identification and evaluation of consistently high rubber
yielding genotypes in native guayule populations. Guayulero
- Lopez Benitez, A. and S. Kuruvadi. 1985. Variation in yield components and
correlations in guayule. Guayulero 7(1&2):19-23.
- Lopez Benitez, A. and S. Kuruvadi. 1987. Variability in rubber content of three
guayule populations in Durango, Mexico. Guayulero 9:(1&2):3-7.
- Naqvi, H.H., and G.P. Hanson. 1983. Observation on the distribution and ecology
of native guayule populations in Mexico. p. 145-154. In: E.C. Gregg, J.L.
Tipton, and H.T. Huang (eds.), Proc. 3rd. Int. Guayule Conf., Pasadena,
California, U.S.A. 27 April-1 May. 1980. Guayule Rubber Soc., Publ. Univ.
- Schloman W.W., Jr. 1988. Rubber additives derived from guayule resin. Ind. Eng.
Chem. Res. 27:712-716.
- Schloman W.W., Jr. and J.P. Wagner. 1991. Rubber and coproducts utilization. p.
287-310. In: J.W. Withworth and E.E. Whitehead (eds.), Guayule natural rubber.
Office of Arid Lands Studies. Univ. Arizona, Tucson.
- Thames, S.F. and J.P. Wagner. 1991. Recent advances in guayule coproduct
research and development. p. 311-350. In: J.W. Withworth and E.E. Whitehead
(eds.), Guayule natural rubber. Office of Arid Lands Studies. Univ. Arizona,
Table 1. Guayule morphologic characteristics at the three sites.
| ||Height (cm) ||Spread (cm)|
|Site ||Locality ||Mean ||Range ||Mean ||Range|
|1 ||Atenco, Coahuila ||50.5 ||42-61 ||57.1 ||46-71|
|2 ||Rocamontes, Coahuila ||52.3 ||48-58 ||55.4 ||48-63|
|3 ||Noria, Zacatecas ||53.5 ||42-64 ||57.9 ||37-66|
|Significance ||nonsignificant ||nonsignificant|
Table 2. Mean values for guayule physiologic characteristics at
** NS = Significant at 1% level (**) or nonsignificant (NS).
|Site ||Total dry weight (g) ||Rubber (%) ||Resin (%) ||Iodine value (%) ||Bagasse (%) ||
|1 ||492 ||10.6 ||12.9 ||29.0 ||76.4 ||6.5|
|2 ||723 ||9.6 ||13.7 ||35.7 ||76.8 ||6.2|
|3 ||761 ||9.7 ||11.9 ||42.8 ||78.4 ||6.9|
|Significance ||** ||NS ||** ||** ||** ||**|
Fig. 1. Map of the guayule growing region in Mexico and localization of
the three analysis sites.
Fig. 2. Relationship between resin content and iodine value for the
plants from the three sampling sites.
Fig. 3. Ternary diagram correlating rubber, resin and iodine value.
Last update August 21, 1997