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Kuruvadi, S. and D. Jasso de Rodriguez. 1993. Rubber and resin content in the bark and wood portions of the root stem and branches in guayule. p. 345-346. In: J. Janick and J.E. Simon (eds.), New crops. Wiley, New York.

Rubber and Resin Content in the Bark and Wood Portions of the Root Stem and Branches in Guayule

Sathyanarayanaiah Kuruvadi and Diana Jasso de Rodriguez

  1. MATERIALS AND METHODS
  2. RESULTS AND DISCUSSION
  3. REFERENCES
  4. Table 1
Guayule (Parthenium argentatum Gray), a perennial shrub, is a potential source of natural rubber for the arid zones of Mexico and other countries. Natural rubber is superior to synthetic rubber derived from petrochemicals and is preferred where low heat buildup, elasticity and resilience are necessary (Fangmeir et al. 1984).

Rubber in guayule occurs as a colloidal suspension in the individual cells in the tissues of cortex and vascular rays of phloem and xylem (Foster et al. 1980). The bark portions of the roots, stems, and branches contain the majority of the rubber (Estilai 1987) and branches contain a higher percentage of rubber and resin than the main stem and roots (Jasso and Kuruvadi 1991). The objective of this investigation was to determine the variability of rubber and resin content in the bark and wood portions of root, stem, and branches and to identify higher rubber yielding lines associated with the production of thick bark.

MATERIALS AND METHODS

Ten accessions were selected from the local germplasm collection of guayule and were seeded in the greenhouse. Fifteen day old seedlings were transplanted individually in polyethylene bags containing approximately 500 g of sieved and fumigated soil and irrigated when necessary. After 65 days of growth in the greenhouse, the seedlings of each accession was transplanted individually at the Dryland Experimental Station, Ocampo, Coahuila, Mexico, using a spacing of 80 cm between rows and 100 cm between plants within a row. When the plants were approximately 32 month old, three entire plants were sampled per treatment. The leaves, peduncles, dried inflorescences, and small branches were pruned and the root system was cleaned. Then each plant was sectioned into three parts: root system, main stem, and branches. The bark and wood tissue were separated from each part by hammering lightly; 5 g of ground sample of each tissue was utilized for quantitative estimation of rubber and resin content using standard soxhlet extraction procedure. The means of rubber and resin in the three plant parts and two tissues were analyzed statistically using completely randomized block of three factor 10 x 2 x 3 (10 entries, 2 tissues, and 3 plant parts) factorial design.

RESULTS AND DISCUSSION

The analysis of variance (not presented) indicated significant differences for percent rubber, percent resin, and diameter of bark and wood tissues between genotypes, between three plant parts, and two tissues indicating that the ten accessions of this investigation differed greatly with respect to the diameter of bark, wood, and their rubber and resin concentration (Table 1). Selection and breeding could further improve these traits.

Rubber percent varied from 3.94 to 11.42% (root), 4.80 to 12.23% (stem), and 4.92 to 11.01% (branches) in the bark, and ranged from 0.38 to 1.55% (root), 0.46 to 4.44% (stem), and 0.72 to 5.00% (branches) in the wood. The mean percent rubber was 7.3% for the bark and 1.4% for wood tissue in the three plant parts; the bark contained 421% more rubber than wood tissue. The total bark and wood portions of these genotypes contain approximately 83.8 and 16.2% of the rubber in the plant. Estilai (1987) estimated that the bark of the plant of guayule contains about 70 to 85% of the rubber in the plant depending on the genotype. Maximum percent rubber was observed in accession 4599 (7.6%), followed by accessions 4580 (5.7%), 4144 (4.8%), 4358 (4.7%), and 4443 (4.3%).

Resin is another important byproduct of guayule; average resin percentage was 11.9 for the bark and 4.3 for wood. The total bark and wood tissue of these accessions contains nearly 73.4 and 26.6% resin in the plant. Superior genotypes identified were 4144, 4443, 4130, 4580, and 4338 which ranged from 8.2 to 9.6% resin.

The thickness of the bark is one of the important characters influencing the total production of rubber and resin in the plant. The mean thickness of the bark was 0.13 cm (root), 0.42 cm (stem), and 0.23 cm (branches). Superior genotypes for bark diameter were 4144, 4161, 4338, and 4597 (root); 4123, 4144, and 4599 (stem); and 4597, 4144, and 4161 (branches). Accession 4144 contained thicker bark in the three parts of the plant studied.

The majority of the rubber and resin accumulation occurs in the bark of the plant. Hence in breeding, high priority should be given to combining bark thickness, higher rubber percent and high biomass yield.

REFERENCES

Table 1. Mean of rubber and resin content in the bark and wood portions of the root, stem, and branches in ten guayule accessions.

Root Stem Branch
Accession Bark Wood Bark Wood Bark Wood
Rubber (%)
4123 4.91 0.56 6.79 0.91 8.13 0.72
4130 5.79 0.95 7.97 0.46 5.75 0.94
4144 6.62 1.09 8.28 1.44 7.76 3.64
4161 3.94 0.62 4.80 1.03 4.92 1.55
4338 5.48 0.56 5.35 0.84 6.64 0.86
4358 9.53 0.38 8.92 0.70 7.35 1.05
4443 5.86 0.73 7.37 1.12 7.91 2.99
4580 8.60 0.70 10.57 3.19 9.98 1.12
4597 3.94 0.62 4.80 1.03 4.92 1.55
4599 11.42 1.55 12.23 4.44 11.01 5.00
Mean 6.61 0.78 7.71 1.51 7.44 1.94
Resin (%)
4123 11.78 2.68 11.79 3.59 11.09 3.64
4130 13.49 4.58 11.91 4.38 12.17 5.23
4144 11.68 5.81 12.82 6.46 13.47 7.23
4161 14.92 2.84 13.46 3.19 9.84 3.44
4338 11.59 4.55 12.36 4.66 10.29 5.89
4358 12.54 2.05 10.60 3.45 10.35 2.79
4443 15.03 4.19 13.37 5.20 12.25 6.57
4580 12.21 4.67 12.22 5.64 11.34 5.09
4597 11.77 3.13 11.81 3.59 11.08 3.62
4599 9.05 3.09 10.04 3.51 11.50 5.49
Mean 12.41 3.76 12.16 4.37 11.34 4.90

Last update April 18, 1997 aw