Table of Contents
Estilai, A. and M.C. Shannon. 1993. Salt tolerance in
relation to ploidy level in guayule. p. 349-351. In: J. Janick and J.E. Simon
(eds.), New crops. Wiley, New York.
Salt Tolerance in Relation to Ploidy Level in Guayule
Ali Estilai and Michael C. Shannon
- RESULTS AND DISCUSSION
- FUTURE PROSPECTS
- Table 1
Guayule (Parthenium argentatum Gray) is a promising alternative to
rubber tree (Hevea brasiliensis Muel. Arg.) for production of natural
rubber in semiarid regions of the world. For the United States, which is
totally dependent on foreign sources of natural rubber, developing guayule as a
commercial crop should be a high priority. A domestic source of natural rubber
is vital to our national defense and helps balance the budget by reducing the
one billion dollars spent annually for the imports of Hevea rubber from
Guayule grows naturally in the semiarid Chihuahuan Desert region of north
central Mexico and the Big Bend area of Texas in the southwestern United
States. The native stands are restricted to outwash fans and rocky slopes of
calcareous soils. In general, guayule is considered to be only slightly
tolerant to soil salinity (Hammond and Polhamus 1965). Although guayule seeds
germinate successfully in highly saline solutions of up to 22 dS/m, seedling
emergence is reduced severely when saline waters are used for irrigation
(Miyamoto et al. 1984). Salinity of irrigation water has been reported to
decrease rubber yield and water use efficiency (Miyamoto and Bucks 1985).
Experiments conducted in the 1940s at Texas indicated that salinity greater
than 3.3 dS/m would be unsuitable for guayule culture (McGinnies and Mills
1980). In a more recent study, conducted at Brawley, California, guayule
appeared more salt tolerant than many crops that were considered tolerant at
the 6 dS/m level (Maas et al. 1986). The apparent disagreement between the
findings of the two studies is due to the high sodium content found in the
Texas water versus the high calcium content in the California water (Nakayama
et al. 1991). Greenhouse sand culture experiments have shown the detrimental
effects of high sodium concentration as compared to calcium on guayule growth
(Wadleigh and Gauch 1944). No statistically significant interaction effects
were found between plant population and salinity (Hoffman et al. 1988).
Salt-tolerant guayule cultivars are needed for economic production of rubber on
marginal lands and in areas with low quality saline water. The available
guayule germplasm which is being used to develop new guayule cultivars are
2n = 36, 54, or 72 (Bergner 1944, 1946; Stebbins and Kodani 1944).
Plants with 2n = 36 are considered to be diploid (Bergner 1944; Estilai
et al. 1985; Hashemi et al. 1989). Diploids reproduce sexually and,
because of a sporophytic system of self-incompatibility, they produce seed by
cross-pollination (Gerstel 1950; Estilai 1984). Plants with 2n = 54 and
72 are polyploid (triploid and tetraploid, respectively), and their mode of
reproduction is by facultative apomixis, the simultaneous occurrence of sexual
and apomictic modes of reproduction (Esau 1944; Gardner 1947; Powers and
Rollins 1945). Information on salt tolerance of guayule plants with different
chromosome number is unavailable. The primary objectives of this study were to
compare diploid, triploid, and tetraploid guayule germplasm, irrigated with
saline water, for important agronomic traits and to identify salt tolerant
individuals for development of improved cultivars.
Open-pollinated seeds from diploid, triploid, and tetraploid guayule germplasm
were planted in a greenhouse at the University of California, Riverside in
January 1989 following procedures described previously (Estilai and Waines
1987; Estilai 1991). Seedlings were hand-transplanted into experimental plots
at Brawley, California on May 24, 1989. The experimental design was a
randomized complete block with four replications. Each entry in a replicate
was planted in a plot consisting of two rows, each 16 m long, with the interrow
and interplant spacing of 1 m and 0.45 m, respectively. Approximate population
density was 22,200 plants/ha. Experiments were surrounded by a row of border
Seedlings were irrigated with normal water until Nov. 6, 1989 when the first
measurements were obtained for plant height and width. Plots were then
irrigated with saline water of electrical conductivity of 7.5 dS/m. Prior to
harvest on Feb. 26, 1991 (when plants were 21 months old), height and width
were measured for 10 plants per plot. The 10 plants were cut at 0.05 m above
ground, leaves and peduncles removed, and plants weighed and chipped.
Immediately after chipping, two samples were taken to determine percent dry
weight and rubber and resin contents. Samples used to determine the percent
dry weight were dried in a forced air oven at 75°C and reweighed.
Samples used for rubber and resin analyses were stored in a freezer and later
were ground in the presence of liquid nitrogen. Resin and rubber were
extracted from the finely ground plant materials using acetone and cyclohexane,
respectively. Detailed procedures for determination of rubber and resin
contents have already been reported (Black et al. 1983; Estilai and Mayhew
Table 1 compares the three germplasm lines for nine agronomic traits. The
polyploid germplasm was significantly superior to the diploids for all traits.
The triploid and tetraploid germplasm were similar in performance except for
resin content and resin yield. The triploid germplasm had the highest annual
resin content of 10.7% and the highest resin yield of 420 kg/ha. Diploid,
triploid, and tetraploid germplasm, respectively, produced 60, 64, and 40% more
resin than rubber (Table 1). Resin is an important co-product, and may provide
an additional revenue for guayule commercialization. Possible applications of
resin include use as an adhesion modifier for strippable coatings and as wood
Annual rubber yield, the most important trait for guayule commercialization,
varied from a minimum of 125 kg/ha for the diploid germplasm to a maximum of
256 kg/ha for the triploid germplasm. These levels of productivity are far
below the annual rubber yield of 1,000 to 1,500 kg/ha needed to make guayule a
successful irrigated crop in prime agricultural lands. However, considering
the reduced value of lands in semiarid regions and lower costs for the low
quality saline water, annual rubber yield of 500 kg/ha may be acceptable for
low input agriculture.
The guayule germplasm showed variation for all traits studied. More than 20
plants with annual rubber yield of 40 g (potential rubber yield of 500 kg/ha)
were identified and will be used to develop cultivars with increased rubber
production under irrigation with saline water.
The variation observed for salt tolerance among the germplasm with different
chromosome number suggests the possibility of selecting ecotypes for arid,
semiarid, and marginal lands. This variability also provides suitable material
to study the genetic basis and the physiological nature of salt tolerance in
- Bergner, A.D. 1944. Guayule plants with low chromosome numbers. Science
- Bergner, A.D. 1946. Polyploidy and aneuploidy in guayule. USDA Tech. Bul.
918. U.S. Government Printing Office, Washington, DC.
- Black, L.T., G.E. Hamerstrand, F.S. Nakayama, and B.A. Rasnik. 1983.
Gravimetric analyses for determining resin and rubber content of guayule.
Rubber Chem. Technol. 56:367-371.
- Esau, K. 1944. Apomixis in guayule. Proc. Natl. Acad. Sci. (USA)
- Estilai, A. 1991. Biomass, rubber, and resin yield potentials of new guayule
germplasm. Bioresource Tech. 35:119-125.
- Estilai, A., and R.C. Mayhew. 1990. Automated gravimetric analyses of guayule
rubber and resin contents. El Guayulero 12:5-11.
- Estilai, A. and J.G. Waines. 1987. Variation in regrowth and its implications
for multiple harvest of guayule. Crop Sci. 27:100-103.
- Estilai, A., A. Hashemi, and V.B. Youngner. 1985. Genomic relationship of
guayule with Parthenium schottii. Amer. J. Bot. 72:1522-1529.
- Estilai, A. 1984. Inheritance of flower color in guayule. Crop Sci.
- Gardner, E.J. 1947. Studies on the inheritance of apomixis and sterility in
the progeny of two hybrid plants in the genus Parthenium. Genetics
- Gerstel, D.U. 1950. Self-incompatibility studies in guayule. II.
Inheritance. Genetics 35:482-506.
- Hammond, B.L. and L.G. Polhamus. 1965. Research on guayule (Parthenium
argentatum): 1942-1959. USDA Tech. Bul. 1327. U.S. Government Printing
Office, Washington, DC.
- Hashemi, A., A. Estilai, and J.G. Waines. 1989. Cytogenetics and reproductive
behavior of induced and natural tetraploid guayule (Parthenium
argentatum Gray). Genome 32:1100-1104.
- Hoffman, G.J., M.C. Shannon, E.V. Maas, and L. Grass. 1988. Rubber production
of salt-stressed guayule at various populations. Irrigation Science
- Maas, E.V., T.J. Donovan, L.E. Francois, and G.E. Hamerstrand. 1986. Salt
tolerance of guayule, p. 101-107. In: D.D. Fangmeier and S.M. Alcorn (eds.).
Guayule a natural rubber source. Guayule Rubber Society.
- McGinnies, W.G. and J.L. Mills. 1980. Guayule rubber production. The world
war II emergency rubber project: A guide to future development. Office of Arid
Lands Studies, Tucson, AZ.
- Miyamoto, S. and D.A. Bucks. 1985. Water quantity and quality requirements of
guayule: Current assessment. Agr. Water Manag. 10:205-219.
- Miyamoto, S., K. Piela, J. Davis, and L.G. Fenn. 1984. Salt effects on
emergence and seedling mortality of guayule. Agron. J. 76:295-300.
- Nakayama, F., D.A. Bucks, C.L. Gonzalez, and M.A. Foster. 1991. Water and
nutrient requirements of guayule under irrigated and dryland production, p.
145-172. In: J.W. Whitworth and E.E. Whitehead (eds.). Guayule natural
rubber. Office of Arid Lands Studies, Tucson, AZ.
- Powers, L., and R.C. Rollins. 1945. Reproduction and pollination studies on
guayule, Parthenium argentatum Gray and P. incanum H.B.K. Amer.
Soc. Agron. J. 37:96-112.
- Stebbins, G.L. and M. Kodani. 1944. Chromosomal variation in guayule and
mariola. J. Hered. 35:162-172.
- Wadleigh, C.H. and H. G. Gauch. 1944. The influence of high concentrations of
sodium sulfate, sodium chloride, calcium chloride, and magnesium chloride on
the growth of guayule in sand cultures. Soil Sci. 58:399-403.
Table 1. Comparison of diploid, triploid, and tetraploid guayule
entries for nine agronomic traits.
zRow means followed by the same letter are not significantly
different at the p = 0.05 level as determined by Duncan's new multiple range
| ||Guayule entries|
| ||Diploid ||Triploid ||Tetraploid|
|Plant traits ||Range ||Mean ||Range ||Mean ||Range ||Mean|
|Height (cm) ||47-66 ||56.5az ||52-64 ||59.5a ||48-67 ||60.5a|
|Width (cm) ||54-69 ||61.8a ||65-75 ||69.5b ||62-76 ||70.5 b|
|Dry weight (kg ha-1 yr-1) ||2,029-2,689 ||2,334a ||3,590-4,351 ||3,856b ||3,513-4,338 ||3,758b|
|Rubber content (%) ||4.9-5.7 ||5.3a ||6.3-7.2 ||6.6b ||6.3-6.8 ||6.5b|
|Resin content (%) ||7.9-9.4 ||8.6a ||9.2-12.2 ||10.7b ||7.9-10.3 ||9.2c|
|Rubber+resin (%) ||12.9-14.6 ||14.0a ||15.9-18.5 ||17.5b ||14.4-16.9 ||15.7c|
|Rubber yield (kg ha-1 yr-1) ||105-147 ||125 a ||224-279 ||256b ||228-272 ||245b|
|Resin yield (kg ha-1 yr-1) ||178-241 ||200 a ||332-503 ||420b ||277-380 ||345c|
|Rubber + resin yield (kg ha-1 yr-1) ||296-388 ||325a ||574-781 ||677b ||506-654 ||590c|
Last update April 18, 1997