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New lines raise the commercial potential of guayule

Premawansa Dissanayake, Doug George and Madan Gupta

School of Agronomy and Horticulture, University of Queensland Gatton, QLD 4343, Australia Email p.dissanayake@uq.edu.au

Abstract

Guayule (Parthenium argentatum Gray) is a potential source of commercial natural rubber. In an effort to commercialise guayule, improved lines with high yielding and fast growing ability have been released. The objective of this study was to evaluate the performance of improved lines in Australia. Performance of improved lines AZ-1, AZ-2, AZ-3, AZ-5 and AZ-6 were evaluated. Previously developed guayule lines N 565 and 11591 were used as controls. Seedlings from these lines were raised in a glasshouse for three months and later transplanted in a field experiment in early September 2001. After 17 months, plant dry-matter production, rubber and resin content, and yields were analysed. Plant dry matter, rubber and resin yields were significantly different among lines. Of the five lines, AZ-1, AZ-2 and AZ-5 produced rubber yields of 620, 550 and 560 kg/ha respectively and these yields were significantly greater than for N 565 (371 kg/ha) and 11591 (391 kg/ha). AZ-1 and AZ-2 also produced significantly higher resin yields, 727 kg/ha and 668 kg/ha respectively, than those for N 565 (436 kg/ha) and 11591 (325 kg/ha). Rubber and resin yield increase of lines, AZ-1 and AZ-2, were in the range of 41-68% and 53-123% respectively over N 565 and 11591.

Media summary

Desert shrub, guayule, is a potential source of natural rubber. Newly released lines evaluated at the University of Queensland show promising results of guayule’s feasibility as a commercial crop.

Key Words

Parthenium argentatum, commercialisation, improved lines, rubber, resin.

Introduction

Guayule is a potential alternative to Hevea to produce commercial natural rubber. It is a perennial, woody shrub native to the Chihuahuan desert of Northcentral Mexico and Southwest Texas (Whitworth and Whitehead 1991).

Natural rubber (cis-1,4-polyisoprene), due to its high performance properties, is an essential raw material used in a variety of products. The high performance qualities include resilience, elasticity, abrasion resistance, efficient heat dispersion, impact resistance, and malleability at cold temperatures (Cornish 2001). Annual consumption of natural rubber is over 6 million tons, which is about 40% of the total rubber used in the world (Auchter et al. 2000).

Today, natural rubber consumed in the world comes entirely from tropical rubber tree, Hevea brasiliensis. It is known to cause a life-threatening Type I latex allergy which is triggered by the presence of protein in the latex (Siler and Cornish 1994). The quality of rubber produced from guayule is equivalent to that from Hevea. Moreover, guayule latex is hypoallergenic (Siler and Cornish 1994) and therefore suitable to produce high value latex products (Cornish and Sile 1996). However, low annual rubber yields has been a main barrier for guayule in its commercial use (Ray et al. 1990). Plant breeding programs were successful in developing high yielding lines. As a recent effort, the Agricultural Research Service (ARS) of the United States Department of Agriculture (USDA) and The University of Arizona jointly released six improved lines of guayule that have high yielding ability and fast regrowth after harvest (Ray et al. 1999).

Australia has the favourable climatic conditions to grow guayule (Nix 1986). Stewart and Lucas (1986) reported that the potential area suitable for guayule production in Australia is more than five million hectares. Given adequate performance of improved guayule lines and improvements in rubber processing techniques, Australia has a high potential to enter the market. A study was initiated in North East Australia to evaluate the potential of improved lines from the USDA under Australian conditions.

Methods

Improved guayule germplasm released jointly by the USDA, ARS and The University of Arizona were used in this trial (Ray et al. 1999). This germplasm consists of five improved guayule lines, AZ-1, AZ-2, AZ-3, AZ-5 and AZ-6. Earlier released lines N 565 and 11591 were used as controls. Seeds were treated to break dormancy using the method of Naqvi and Hanson (1980). Seedlings from those seeds were raised in a glasshouse for three months and then they were transplanted in the field in September 2001.

The field trial was conducted in the Research Farm at the Gatton Campus of the University of Queensland. The soil type was a Lawes Black Earth, self-mulching cracking clay with less than 0.5% slope. The pH of the soil was 7.9 and soil organic carbon content was 1.2%. The site receives an average annual rainfall of 763 mm which is summer dominant with 68% of rain usually falling between October and March.

The experimental design was a randomised complete block with three replicates. Seedlings were transplanted into plastic mulched raised beds at 1.5 m spacing. Plots consisted of 4 rows, each with 10 plants at 0.35 m spacing. A trickle system was set up to irrigate the plants. Seedlings were irrigated daily during the first week after transplanting and then once a week for three weeks. Thereafter, supplementary irrigation was provided to reduce stress on plants. Nitrogen fertiliser was applied on two occasions with a total of 63 kg N/ha.

When plants were 17 months old, 4 plants from each plot were clipped at ground level to determine plant dry matter (top growth), stem dry matter, resin and rubber contents, and resin and rubber yield. Leaves plus immature and dead branches were removed from the plant. The remaining stems and branches were chipped using a garden shredder to facilitate drying and sampling. The entire biomass from 4 harvested plants from each plot was oven dried at 60C to estimate the total plant and stem dry matter yields. The stem dry matter yield included stem and mature branches. A representative sample of approximately 100 grams of this chipped material was then ground using a Retsch grinding mill. These samples were then analyzed for rubber and resin contents using the method of Black et al. (1983) and revised by USDA, ARS. Rubber and resin yields were calculated using the product of stem dry weight and rubber and resin contents. All data were subjected to analysis of variance and treatment means were compared by Tukey’s simultaneous test at the 5% level of significance.

Results

Plant dry matter production showed significant differences among lines (Table 1). In general the improved lines (AZ-1, AZ-2, AZ-3 and AZ-5) produced more dry matter or tended to produce more dry matter than the controls. Total plant dry matter (excluding roots) of AZ-1 (13.15 t/ha) was significantly greater than N 565 (6.95 t/ha) and 11591 (8.26 t/ha). AZ-2 and AZ-3 were also produced significantly greater plant dry matter than N 565, but not of 11591. Dry matter yields of stem and branches showed similar trends to total dry matter yields. Stem dry matter values of AZ-1 (8.35 t/ha) and AZ-2 (7.53 t/ha) were significantly greater than N 565 (4.59 t/ha) and 11591 (5.12 t/ha). AZ-1 and AZ-2 produced 47 to 82% more stem dry matter yields compared with 11591 and N 565.

Rubber and resin contents and yields showed significant differences among lines (Table 1). Rubber contents of all of the improved lines except AZ-3 were not significantly different from the controls. AZ-3 produced significantly lower rubber content than that of N 565, but not of 11591. Rubber contents of all lines appeared to be higher than those obtained from 2 and 3 year old plants (4.6 – 7.7%) grown in the USA (Ray et al. 1999). This would indicate genotype x environment interaction. Comparatively higher rubber content in Australia compared with the U.S. may be due to periodic moisture stress that favours the synthesis of cis-1,4-polyisoprene (Retzer and Mogen 1947)

Table 1. Mean plant dry matter yield, resin and rubber contents and, resin and rubber yield of five improved guayule genotypes compared with 11591 and N 565 at 17 months

Line

Plant dry matter yield (t/ha)

Stem dry matter yield
(t/ha)

Resin content
(%)

Resin yield
(kg/ha)

Rubber content
(%)

Rubber yield
(kg/ha)

AZ-1

1315a*

835a

86ab

727a

75ab

620a

AZ-2

1138ab

753a

87ab

668ab

74ab

550a

AZ-3

1057ab

679ab

85ab

584abc

69b

467abc

AZ-5

967bc

678ab

80ab

537abc

84a

560a

AZ-6

861bc

595bc

77b

455bcd

83a

506abc

11591

826bc

512bc

64c

325d

73ab

391bc

N 565

695c

459c

94a

436cd

83a

371c

* Means within a column followed by the same letter are not significantly different at the

0.05 level according to Tukey’s simultaneous test.

Rubber yields of AZ-1, AZ-2 and AZ-5 were significantly higher than 11591 and N 565. Rubber yield increases of these lines were in the range of 41% to 67% compared to N 565 and 11591 (Figure 1). A rubber yield of 620 kg/ha for AZ-1 appears to be higher than that produced by two year old plants of AZ-1 (576 kg/ha) grown in Maricopa, Arizona (Ray et al. 1999). For AZ-5, 560 kg/ha in the present study was about 20% lower with that from the U.S.A. (675 kg/ha). Differential yields between the U.S. and Australia may be accounted for by genotype by environmental interaction.

Resin contents of all improved lines were not significantly different to one another but all were superior to 11591 and similar to N 565 except for AZ-6 (Table 1). AZ-1 and AZ-2 produced significantly greater resin yields than the controls due to greater biomass. AZ-3 and AZ-5 also produced significantly greater resin yields than 11591 but N 565. Resin yields of AZ-1 and AZ-2 ranged from 53% to 123% greater than N 565 and 11591.

Figure 1. Increase in rubber yields of new guayule lines compared to control (N 565 and 11591)

Conclusion

All of the improved lines of guayule performed better than 11591 and N 565 growth in a black earth soil in a sub-tropical climate in Australia. In general, greater biomass, rubber and resin yields were found with the improved lines compared with the older USDA lines, N 565 and 11591. Of the five improved lines, AZ-1, AZ-2 and AZ-5 appeared the most promising, having significantly greater rubber yields. In comparison with N 565 and 11591, the minimum yield increases obtained from these lines were 41% and 53% for rubber and resin respectively. AZ-1 produced the greatest biomass, rubber and resin yield. AZ-5 produced the second best results for rubber yield with highest rubber content of 8.4%. Even though AZ-2 tended to produce lower rubber and resin yields than AZ-1, it had the best combination of early vigorous growth, resin and rubber yields.

References

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Nix HA (1986). Land evaluation for potential guayule rubber production in Australia. In: Stewart GA and Lucas SM (Eds.), Potential production of natural rubber from guayule (Parthenium argentatum) in Australia, CSIRO, Australia, pp. 27-58

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Ray DT, Dierig DA, Thompson AE and Coffelt TA (1999). Registration of six guayule germplasms with high yielding ability. Crop Sci. 39, 300.

Retzer JL and Mogen CA (1947). Soil-guayule relationships. J. Am. Soc. Agron. 39(6), 483-512

Siler DJ and Cornish K (1994). Hypoallergenicity of guayule rubber particle proteins compared to Hevea latex proteins. Ind. Crop Prod. 2, 307-313.

Stewart GA and Lucas SM (1986). Potential production of natural rubber from guayule (Parthenium argentatum) in Australia, CSIRO, Australia.

Whitworth JW and Whitehead EE (1991). Guayule Natural Rubber, Office of Arid Lands Studies, The University of Arizona, Tucson, Arizona, USA.

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