F.S. Nakayama

Lesquerella commercialization efforts in the United States

Abstract Lesquerella fendleri (Gray) Wats. is a promising new crop for cultivation in the western United States. Its oil-bearing seed contains high amounts of the hydroxy fatty acid (HFA), lesquerolic acid (C20:1-OH), suitable as a raw material for many types of industrial applications. Currently the U.S. imports castor seed oil as its chief source of HFA, used primarily in the production of lubricants and plastics. Lesquerella could complement castor oil imports as well as provide new applications and products. Lesquerella meal is being tested as a feed source. Other lesquerella species contain varying amounts and types of HFA. L. fendleri appears to be highly cross-pollinated, and as a consequence, considerable genetic variation exists for traits such as seed oil content, HFA, yield, flowering time, and growth habit. Rapid progress is being made toward full commercialization of lesquerella with private companies and government agencies working together in parallel studies on yield improvement and on finding new uses for the seed oil. Cooperative plantings began in 1990 and included 12 ha in central Arizona and Texas. Planting for 1991 has been increased to 30 ha and covered a wider range of climatic and soil conditions. The seed oil from these plantings is being used to formulate and test lubricant and cosmetics products. Agronomic management practices being investigated include planting methods, time of harvest, and irrigation scheduling. Fortunately, existing farm equipment with minor modification can be used for planting and harvesting the crop. Genetic and germplasm improvement studies are also being conducted and covers germplasm evaluation, selection, and hybridization.

Carbon isotopes and carbon turnover in cotton and wheat FACE experiments

The Maricopa cotton and wheat FACE (free-air CO2 enrichment) experiments offer propitious opportunity to quantify carbon turnover. The commercial CO2 (% MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaeqiTdq2aaW% baaSqabeaacaaIXaGaaG4maaaakiaaboeacqGHijYUcqGHsislcaaI% ZaGaaG4naiaacwcaliaad+gaaaa!3FCB!\[\delta ^{13} {\text{C}} \approx - 37\% o\]) used to elevate CO2 concentration in field plots provided a strongly 13C-depleted tracer. Soil CO2 and δ 13C of soil organic carbon (SOC) in CO2-enriched and Control plots were measured between the final cotton FACE project (October 1991) and the end of the second wheat experiment (June 1994). The initial 13C-depletion in SOC of cotton FACE plots (measured by the difference in δ 13C between FACE and Control plots) persisted at the same level (1.9‰) 1.5 years after the experiment ended. A similar depletion was observed in soil CO2 evolved in the same plots, indicating ongoing decomposition of the new SOC. The SOC δ 13C of wheat plots before and after two growing seasons showed increasing 13C-depletion in FACE relative to Control. Isotopic mass balance was consistent with 5–6% new carbon input from the two wheat crops. This is lower than the 12–13% calculated for FACE cotton and perhaps a consequence of the larger root system of cotton or the 3-year duration of the cotton experiments versus 2 years for the wheat.

Latex quantification in guayule shrub and homogenate

Commercial development of hypoallergenic latex from Parthenium argentatum (Gray), especially for the manufacture of latex medical and household goods, requires specific knowledge on the best lines, agronomic practices and storage conditions for the generation of maximal latex yield. Development can proceed only by using standard, accurate analytical techniques for latex extraction and quantification. In this paper, we describe a latex extraction method that parallels the proposed commercial extraction process and we demonstrate that different extraction equipment can introduce large variations in the apparent amount of extractable latex. An evaluation protocol for testing and optimizing the efficiency of alternative extraction equipment is presented. Also, we describe a rapid latex quantification method for use with shrub and shrub homogenates, confirm its accuracy with tissue balance analysis and show how it can be used to quantify latex in materials with unusually low latex content. The reproducibility of the basic method and of a variation of the method, were determined by analysis of identical homogenates by researchers at different locations.

Planting date and nitrogen fertilization effects on lesquerella production

Abstract Lesquerella (Lesquerella fendleri (Gray) Wats.) produces seed containing hydroxy fatty acids similar to castor oil and has good commercial potential. An important step in the commercialization of this plant for the southwestern desert regions of the United States is the development of an efficient agronomic production system. Field experiments were conducted during the 1991–1992, 1992–1993, and 1993–1994 growing seasons at the University of Arizona, Maricopa Agricultural Center, Maricopa, Arizona to determine the effect of planting date and nitrogen fertility on lesquerella seed yield. Results indicate that fall plantings are necessary to obtain high seed production. September plantings generally produced higher yields than the October or November plantings. February plantings produced low yields and appear to be too late for a growing season that ends in June in central Arizona. In all years, lesquerella responded to nitrogen (N) fertilizer. The addition of 60 to 120 kg N/ha increased biomass and seed yields. Nitrogen fertilizer did not affect 1000-seed weight, but decreased seed oil content in the 1993–1994 planting. There is evidence that increasing the N application rate decreases seed oil content in lesquerella.

Heritability of height, width, resin, rubber, and latex in guayule (Parthenium argentatum)

Abstract Plant breeding in guayule, a rubber and latex producing plant, has not been as effective as predicted or desired. A surprisingly large amount of variability has been reported in this apomictic crop for traits such as plant height, width, resin, rubber, and latex contents. This study was designed to calculate the proportion of the total measured variability due to the environment and the proportion due to genetic influences within and between three-released germplasm lines. Plant heights were measured at 1, 2 and 3-years-of-age; plant width, and latex contents at 2 and 3-years-of-age; and resin and rubber content at 2-years-of-age. Broad-sense-heritabilities were estimated for each trait and year by dividing the genotypic by the total variance. To estimate the genetic component of the measured variance for each trait, the environment effects (variance from clonally propagated plants) were subtracted from the total variance (variance from open-pollinated (OP) seed propagated plants). In general, the variances of the means for the measured traits were lower in the clonally propagated plants compared with the apomictic OP seed propagated plants. The heritability estimates calculated for each trait differed from year to year. For instance, heritability for plant height was estimated in line AZ-2 to be 0.84 at 1 year of age; 0.47 at 2 years of age; and 0.0 at 3 years of age. These values imply that a large portion of the observed variation in this line is attributed to genetic effects in the first 2 years of growth. As the plant grows over several seasons, the environment effects compound, masking the genetic effects, making effective selection choices more difficult. Heritability for latex content for the same line was estimated to be 0.97 for the second year and 0.55 for the third year. Selections for the measured traits in this study appear to be most effective during the first and second years of growth, with effectiveness diminishing during the third year. Most selections previous to this study were performed between 3 and 5 years of growth, thus suggesting one reason for the lack of significant progress in most breeding programs.

Post-harvest stability of latex in different sizes of guayule branches.

Abstract Commercial development of hypoallergenic latex from Parthenium argentatum (Gray) for the manufacture of latex medical and household goods, is hampered by the lack of information on latex stability in the harvested shrub prior to processing. In this paper, we investigate the effect of post-harvest storage on extractable latex content of guayule branches. We found that harvested guayule branches can be stored at 4°C for at least 2 weeks without compromising latex yield, provided that dehydration does not occur. When stored hydrated at 4°C, latex levels declined between 2 and 5 weeks in all branch sizes with the most latex lost from the smallest branches and the least from the medium ones. The latex levels declined due to a combination of conversion of latex into solid rubber in situ and rubber degradation, depending upon the branch size. Overall rubber degradation from the latex and solid rubber pools in the branches was substantial in the smallest branches, but was not seen in the largest. Latex levels declined more quickly at warmer temperatures, even when the branches were hydrated, and were adversely affected by even slight dehydration.

Biobased composition boards made from cotton gin and guayule wastes: select physical and mechanical properties

Using biomass materials such as cotton gin byproducts (CGB) and guayule wastes in value-added products can help the economics of these crops, and additionally, aid in alleviating waste management and environmental problems. A study was conducted to assess important physical and mechanical properties of composition boards made from select CGB and guayule waste. Boards were made from five different ratios of cotton gin and guayule wastes: 100 : 0, 75 : 25, 50 : 50, 25 : 75, and 0 : 100. Overall, the biobased CGB and guayule waste boards showed great potential. However, refinement is needed to further enhance the performance of these biomasses for composite board applications.