Anson E. Thompson

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.

Collection and evaluation of new Lesquerella and Physaria germplasm

Lesquerella and the closely related genus Physaria are prime candidates as a new, alternative source of hydroxy fatty acids (HFA) for industrial uses. At present, castor oil is the only natural source of these HFA for commerce. To expand the germplasm base of these taxa for our breeding program and the National Germplasm System (NPGS), we collected species from a wide geographic region in the United States. In 1993, 44 accessions of Lesquerella fendleri, 38 accessions from nine other Lesquerella species, and three accessions of two different Physaria species were obtained. In 1994, 41 additional accessions of L. fendleri and 51 accessions of ten other Lesquerella species were collected. A total of 20 different species of Lesquerella and two Physaria species were collected over the two years. Oil characteristics and seed size of eight of these Lesquerella and one Physaria species have not previously been reported. Twelve of these taxa have not been available in the NPGS. Populations of L. fendleri collected in Arizona had higher seed-weights than those collected from Texas and New Mexico. Some of the new accessions had seed-weights higher than germplasm presently in the USDA-ARS breeding program. Diverse growth habits were found in populations from all three states. We believe that other species of Lesquerella and Physaria could later be developed as a source of HFA in regions other than the arid southwestern United States. Accessions of Lesquerella douglasii had the same or higher seed-oil content than L. fendleri and also higher seed yields. Two accessions of Physaria newberryi had seed-weights that ranged between 4.5 and 6.2 g/1000 seeds compared to that of 0.25 to 1.1 g/1000 seeds for L. fendleri. Seed-oil contents of P. newberryi averaged 30.8% compared to 23.8% for L. fendleri. Preliminary seed increase and evaluation of oil content and composition were completed on 14 L. fendleri populations from the 1993 collection under field conditions in Phoenix, Arizona. Accessions were compared to the original populations collected in 1993 and 1994 for growth habit, seed size, and seed-oil content and quality.

Characterization of Vernonia galamensis germplasm for seed oil content, fatty acid composition, seed weight, and chromosome number

Abstract Vernonia galamensis (Cass.) Less. has potential for domestication as a new industrial oilseed source of natural epoxy fatty acids. Thirty-four accessions from the six subspecies of the Vernonia galamensis complex were characterized for seed weight, seed oil content, and fatty acid composition. The mean seed weight of the six subspecies was 3.42 g/1000 seeds, with a range of 2.46 g to 5.43 g for ssp. mutomensis and ssp. afromontana, respectively. The mean seed oil content for the six subspecies was 30.8%, ranging from 25.1% to 39.2% for ssp. mutomoensis and ssp. lushotoensis, respectively. The 18:1 epoxy fatty acid (vernolic acid) was predominant. The mean vernolic acid content for the six subspecies was 72.5%, and ranged from 66.9% to 76.6% for ssp. mutomoensis and ssp. lushotoensis, respectively. Within the four varieties of ssp. galamensis, in which most of the current domestication effort is centered, oil contents ranged from 31.8% to 38.4%, and 18:1 epoxy fatty acid ranged from 68.0% to 77.0%. Mean levels of other fatty acids within the species were about 14% for linoleic acid (18:2), 7% for oleic acid (18:1), and from 2 to 3% for both palmitic acid (16:0) and stearic acid (18:0). The basic chromosome number for Vernonia galamensis was found to be n = 9. It was concluded that selection for improved levels of both oil and vernolic acid contents should be possible within a germplasm enhancement and plant breeding program.

Initial selection and breeding of Lesquerella fendleri, a new industrial oilseed

Abstract Considerable research and developmental efforts are being devoted by both the public and private sectors to commercialize Lesquerella fendleri as a new industrial oilseed crop for the production of hydroxy fatty acids. Selection and breeding research initiated in 1984 at the USDA-ARS, US Water Conservation Laboratory, Phoenix, Arizona has made progress in increasing seed, oil and lesquerolic acid yields. Yields of 1700 kg/ha of seed, 30% oil and 59% lesquerolic acid have been obtained in replicated trials. Single plant selections developed during the interium are traceable to two populations: one to a single collection made in Arizona, PI 331165, and the other to nine different accessions collected from various sites in Texas. Variation among selections within each population exhibited relatively the same amount of genetic variability. Neither population appeared to be superior as a source of variation. The need for acquisition and utilization of new sources of germplasm is indicated. Topcross yield performance of six selected lines appeared to be superior to that of comparable halfsib family progeny, validating the existence of heterosis, which is expected due to the high degree of natural cross pollination observed. These data should serve as a benchmark upon which future progress in varietal and population development can be measured.

Germplasm development of Vernonia galamensis as a new industrial oilseed crop

Abstract Genetic transfer of the day-neutral flowering habit found in Vernonia galamensis ssp. galamensis var. petitiana [A 20295 (V 029)] has been successfully accomplished by intraspecific hybridization. Crosses were made in 1990–1991 utilizing var. petitiana as the female parent and five other accessions from the V. galamensis complex as male parents. The F 1 progenies of the crosses were grown in the greenhouse in 1991–1992. Single plant selections were made within F 2 and F 3 field-grown populations in 1992 and 1993, respectively, in Arizona and various locations throughout the continental United States. Seed increase of selected F 3 plants was made in Puerto Rico in 1993–1994 for wide-scale evaluation, further selection, and initiation of agronomic crop production research. Selection for rapid germination in the seedling stage in F 2 and F 3 populations was effective in minimizing seed dormancy. Early germination, nine days after planting, increased from 10.9 ± 1.6% for the F 2 s, to 34.3 ± 1.8% for the F 3 s. Among the 59 F 2 crosses grown under long-day conditions in the field in 1992, the percentage of F 2 plants flowering ranged from 31% to 100%, with a mean of 77.3 ± 2.5%. Flowering percentage of F 3 progenies from within 38 crosses increased to 94.2 ± 1.6% with a range of 50% to 100%. Mean seed weights of greenhouse-grown F 1 s was 5.73 ± 0.12 g/1000. Field-grown F 2 s and F 3 s had smaller seed weights, 2.50 ± 0.05 and 2.11 ± 0.06 g/1000, respectively. The F 1 s also had higher seed oil and vernolic acid contents (39.8 ± 0.4% and 80.8 ± 0.4%) as compared to the F 2 s (33.2 ± 0.4% and 62.0 ± 1.0%) and the F 3 s (32.1 ± 0.6% and 64.9 ± 0.8%). The relatively wide range in seed weight, and in oil and vernolic acid contents in both F 2 s and F 3 s demonstrate that directed selection for these yield factors should be effective. High genotype × environment interaction suggests that plant selection and evaluation should be conducted over a range of geographic and climatic conditions within the temperate zone to identify the most favorable production sites. The rapid progress made within the past five years indicates that commercialization of vernonia as a new industrial oilseed could be a reality within the next seven to ten years.

Variation in Vernonia galamensis flowering characteristics, seed oil and vernolic acid contents

Abstract Considerable variation in plant and flower characteristics was observed among seventeen accessions of the Vernonia galamensis (Cass.) Less. complex, including representatives of all but one subspecies. With the exception of ssp. nairobensis, a high percentage of plants of all accessions had flowered by 121 days after planting (DAP) in Arizona on the 9th of January. Mean days to flower for various accessions varied from 37 to 121 days, and those flowering by 121 DAP had mean numbers of capitula ranging from 0.1 to 86 per plant. Fully mature capitula on accessions ranged from 0 to 55%, and plant height varied from 23 to 88 cm at 121 DAP. Seeds of five accessions from three subspecies harvested at full maturity had significantly higher oil and vernolic acid contents, and seed weights than comparable samples harvested at a less mature stage when involucres surrounding maturing seeds were still green in color. Seeds of uniform lots of the day-neutral accession of V. galamensis ssp. galamensis var. petitiana [A 20295 (V 029)], grown at six locations throughout the United States, had highly significant differences in oil percentage (34.5–44.3%), vernolic acid content (61.0–80.0%), and seed weight (1.87–2.91 g/1000). Although environmental factors play a significant role in seed oil and vernolic acid contents, and seed weight, there appears to be no serious constraints to the ultimate domestication and commercialization of vernonia for production in temperate areas. However, considerable genetic improvement is required, and further evaluation, selection, and development of germplasm within various climatic and geographical locations will be necessary to maximize adaptation and yield.

New native crops for the arid Southwest

Agricultural production in the arid Southwest is heavily dependent upon water for irrigation. If current trends of water use continue, the amount of water available to agriculture in the year 2000 will only meet approximately 50% of the needs of currently available irrigated crop land. Development of new crops with low irrigation needs is of highest priority. None of the major crop plants of the world is well adapted to arid lands. However, in the Sonoran Desert, more than 375 species of noncultivated food plants have been identified, and approximately 40 of these served as major local food resources for native people in the region. Research and development of new crops must address the issues of water use, productivity, chemical composition, and quality. Domestication of native species that have evolved and became adapted to arid conditions in the Southwest is considered to be a good strategy. Research and development programs on such native, new crops as guayule, jojoba, and buffalo gourd are well underway. New domestication programs involvingCuphea species for medium-chain fatty acids,Lesquerella species for hydroxy fatty acids,Grindelia camporum for resin production, and interspecific hybrids ofBaccharis for landscape plant materials are described. The role of the USDA Agricultural Research Service, state agricultural experiment stations, and industry in the development of new crops is discussed.

Parent-offspring relationships in apomictic guayule

The genetic base of guayule (Parthenium argentatum Gray) germ plasm that is available is narrow; yet, significant variability has been described within this germ plasm. This variability is surprising because guayule reproduces by facultative apomixis (asexual reproduction by seed), but evidence suggests that progress through selection is feasible. It has been hypothesized that this variation has arisen through periodic sexual reproduction; however, this has not been quantified. This study was designed to describe and compare eight components of yield and the expression of two isozyme systems in twenty parent plants and half-sib, open-pollinated families from each parent. Extensive variation for all characters was found among both the parents and the progeny, with fresh and dry weights being highly correlated to rubber yield. Parent-offspring regressions were not significantly different from zero. This implies low heritabilities for the major components of yield in guayule, and we believe that family selection, rather than single-plant selection, may generate higher-yielding and more genetically uniform lines at an escalated rate than single-plant selection. Periodic sexuality resulting in genetic variation was estimated by differences in isozyme expression within the half-sib families. Fifteen of the twenty progeny families were polymorphic for either esterase or peroxidase or both isozymes. This amount of sexuality is significant, and guayule must be considered an open-pollinated crop. We conclude from this study that we should rethink our breeding procedures to include controlled pollination and family selection.

Effects of field storage on guayule rubber quantity and quality

Abstract Irrigation treatments affected the amount of biomass produced, but not the NR percentage of the plant or the quality or quantity. Different guayule genotypes varied in their rate of rubber degradation over storage time. All lines tested in this experiment decreased in Mw by the end of the storage period, but degradation in some did not occur until the fourth week of storage. An increase in Mw of most lines was seen after the first week of storage, indicating that the enzymatic processes are still functioning beyond the first few hours of harvest, and for some lines, beyond the initial sample taken after one week of field storage. Other lines may follow this same pattern of degradation, but it was not detected by the sampling protocol in this study. Guayule lines 11605, 11619 and interspecific hybrid AZ101, when irrigated between 4 to 7 times per year (50 to 90 cm/year), harvested in early spring, and then stored in the field as whole plants for no more than 2 weeks, would yield optimum rubber qua...