Lesquerella fendleri L., a source of hydroxy fatty acids, is a promising new industrial oilseed crop adapted to the desert Southwest (Thompson 1988). The status of Lesquerella domestication and commercialization is reviewed by Thompson in this volume. Yield data on L. fendleri and other species are needed to establish their potential for temperate agriculture.
New industrial oilseeds crops have, as a general rule, no domestication history beyond the last one or two decades. The lack of domestication histories is not surprising since their industrial use potential was discovered only within the last few decades. The rate of domestication of these species depends on the current agronomic characteristic of the crop. New oilseed crops generally have domestication barrier traits, e.g., seed shattering and seed dormancy. In addition, their germplasm resources may be limited. The rate of commercialization, ignoring factors unrelated to plant improvement, depends on the genetic variation for economically important traits and size of the germplasm resource. There are tremendous differences in genetic variation for traits affecting rates of domestication and commercialization among new oilseeds. These differences ultimately determine whether or not these species will be commercialized.
My objective is to review the domestication and commercialization status of various new industrial oilseeds. There is, however, a need to briefly mention genetic engineering activities in oilseeds, specifically, activities to alter fatty acid phenotypes of suitable commercial oilseed crops, e.g., rapeseed (Brassica napus L.), by transforming them with genes cloned from specialty oilseeds. While there is much research in this area, there is little published information because genetic engineering activities are mainly restricted to the private sector or in the initial stages of development. I am aware of two major projects on the genetic engineering of industrial oilseeds. C.R. Somerville and others have a project at the Michigan State University DOE Laboratory, emphasizing biochemistry and the genetic engineering of crops for new non-food products, e.g., industrial oilseeds (Anonymous 1988). Calgene is conducting a project in the private sector (V. Knauf, pers. commun.). There are others.
Medium-chain, hydroxy, and epoxy fatty acids crops are excellent genetic engineering targets. Seed oils rich in these fatty acids account for approximately 625,000 t/yr (6.25 x 108 kg/yr or 1.38 x 109 lb./yr) of oil not currently produced by American agriculture. Suppose we had crops capable of producing seed oils rich in these fatty acids with seed yields of 2242 kg/ha (2000 lb./a), oil percentages of 35.0%, and seed oil wields of 785 kg/ha (700 lb./a). These crops would occupy 796,178 hectares (1,967,356 acres) and have an annual value, assuming a seed oil price of $0.30/lb., of $414,000,000 or slightly less than half a billion dollars. We need to increase our investment in the domestication and genetic engineering of new industrial oilseed crops to capture these markets.
Cuphea is a genus of approximately 250 undomesticated species native to Mexico and Central and South America (Graham 1988). One species, C. viscosissima, is native to the U.S. Several are adapted to temperate agriculture and have seed oils rich in capric and lauric acid (Graham et al. 1981, Hirsinger and Knowles 1983, Hirsinger 1985). Thus, one possibility for domestic production of lauric and capric oils is through the cultivation of Cuphea. The economical cultivation of Cuphea is, however, presently prevented by the problem of seed shattering.
Seed shattering and seed dormancy usually determine the difference between undomesticated and domesticated forms of a species. The wild progenitors of several seed crops, e.g., wheat (Triticum aestivuum L.), rice (Oryza sativa L.), oats (Avena sativa L.), barley (Hordeum vulgare L.), and sorghum [Sorghum bicolor L. (Moench.)], are characterized by seed shattering (Ladizinsky 1983). Nonshattering phenotypes are simply, inherited in these species and were presumably fortuitously discovered, selected, and fixed in populations sometime within the last 10,000 years (Renfrew 1969). There is no apparent advantage to seed retention in natural populations; however, genetic variation for seed retention was obviously present in wild populations of these species.
Wild populations of Cuphea are characterized by seed shattering and seed dormancy, so domestication depends of finding or inducing genetic variation for these traits. Hundreds of populations in several species have been collected without observing natural variation for seed retention (Graham 1988). Differences in fruit morphology or seed retention have not been observed in recently collected populations of C. tolucana Peyr. (42 populations), C. laminuligera Koehne (8 populations), C. leptopoda Hems. (4 populations), and C. viscosissima Jacq. (50 populations). Continued exploration for seed retention variation is needed; however, finding seed retention variation in Cuphea is not a simple matter. Exhaustive germplasm collection and evaluation in promising species is needed for other equally important reasons and may result in the discovery of genetic variation for seed retention.
Another alternative, given the apparent lack of natural genetic variation for seed retention, is to attempt to induce genetic variation in traits controlling fruit development and seed dispersal. There are, as usual, no guarantees that useful mutants will be induced.
We are using chemical mutagenesis of seeds to induce genetic variation. One or two generations of mutation breeding programs have been completed in various species. We have evaluated M2 populations of C. lutea Rose and C. viscosissima and generated M2 populations in C. carthagenensis (Jacq.) MacBride (n = 8) and C. lanceolata Ait. (n = 6) from ethyl methanesulfonate (EMS) treated seeds. Approximately 10% of the C. viscosissima M2 population of 1000 plants was comprised of macro-mutations. No seed retention mutants were observed. There were no macro-mutations in the C. lutea population. We presume macro-mutations are not observed in C. lutea because of duplicate genes and speculate that C. lutea is a polyploid, probably a tetraploid. Chromosome numbers in C. lutea and C. viscosissima are n = 14 and n = 6, respectively (Graham 1988).
Seed dormancy in C. viscosissima forced us to evaluate a small M2 Population (1000 individuals) in 1988. M2 plants were derived by excising embryos from M2 seed, growing seedlings in the greenhouse, and transplanting to the field. We plan to study larger M2 populations of C. viscosissima once there is a solution to the seed dormancy problem. We effectively used stratification to break dormancy in M1 seed of C. viscosissima but were unable to repeat this with M2 seed. We are restricted to growing one field generation every, two years in C. viscosissima without embryo excision or non-dormant populations.
Seed is dispersed in Cuphea through dorsal splitting of the floral tube and capsule and upward rotation of the placenta (Graham 1988). Seeds are easily freed from the placenta. The fruit or capsule wall is extremely thin and does not protect the seed. The floral tube is sturdy but does not protect the seed once the placenta has rotated upward (Graham 1988). The physical and physiological mechanisms leading to placental rotation, floral tube suture formation, and seed dehiscence have not been investigated.
I envision three mutant phenotypes, natural or induced, leading to increased seed retention. They, are: no placental rotation (rotation minus mutants), no floral tube sutures (suture minus mutants), and strong placenta to seed attachment. Nothing is known about the genetic control of these processes, so there is no way to quantify the likelihood of observing mutants affecting them. This is, of course, always the problem since mutants are needed to work out the genetics!
The domestication potential of at least 30 species has been investigated and promising species have been identified (Hirsinger and Knowles 1983). When the breeding program began at OSU three years ago we were investigating eight)species: C. laminuligera, C. lutea, C. lanceolata, C. wrightii A. Gray, C. viscosissima, C. leptopoda, C. tolucana, and C. carthagenesis. There are no gross differences in seed retention among these species, so other factors have been used to select among them. My objective has been to select a capric and a lauric acid species. The process of species selection has been slowed because of limited germplasm and limited knowledge about species differences (seed yields and genetic variation). Nevertheless, we have settled on a few species.
Insect pollination is required in allogamous species, e.g., C. laminuligera, C. lanceolata , and C. leptopoda. A suitable pollinator for commercial plantings has not been found. Experimental plantings are mainly pollinated by bumblebees. The long floral tubes of allogamous species prevent honeybees from gaining access to the nectar. Bumblebees have long proboscises and are able to forage for nectar. We used leafcutter bees at rates of approximately 120,000 bees/ha in experiments at Medford, Oregon in 1987 and 1988. We observed limited leafcutter bee activity and experienced very poor seed set on allogamous species in these experiments. Commercial production of the allogamous species is not possible without solving the insect pollinator problem. A simple solution seems unlikely. We are, therefore, discontinuing breeding activities in allogamous species. Breeding efforts in autogamous species have, until 1988, been hindered by limited germplasm resources.
C. lutea, C. viscosissima, C. tolucana, C. wrightii, and C. carthagenesis, among the autogamous species, have been most intensively investigated. C. lutea and C. wrightii (n = 22) are undoubtedly allotetraploids. Seed treatments with chemical mutagens in C. wrightii, like those in C. lutea, failed to generate macro-mutations (Campbell 1987). Thus, "observable" macro-mutations may not be generated, at least not at acceptable frequencies, in these species.
The main criteria we are using to select among species, besides those criteria already mentioned, is adaptation and seed yield. We have seed yield data on C. lutea and C. wrightii but not on C. viscosissima and C. carthagenesis. Seed resources of the latter two species have been limited. Furthermore, seed dormancy has limited seed increases in C. viscosissima and prevented the establishment of C. viscosissima entries in yield experiments. Seed wields of C. lutea have exceeded those of C. wrightii in Oregon. Seed wields of C. lutea from swathing on tarps and subsequent threshing ranged from 400 to 1200 kg/ha at different harvest dates in 1987 at Medford, Oregon. There are two important points about these seed yields. First, experimental seed yields are undoubtedly substantially greater than those achieved by combining. Harvesting methods are under research and have not been standardized or optimized. These seed yield data are useful for comparing species but not for predicting yields under commercial cultivation. Second, single harvest seed yields represent about 10-40% of the seed yield potential of equivalent populations with seed retention.
Economical seed yields cannot be obtained without seed retention. The crop could be harvested after a killing frost and seed yield could accumulate to the end of the growing season if seed were retained. Thus, capturing seed yield is a problem but seed yield per se is apparently not a problem.
C. viscosissima was grown in a yield trial for the first time in 1988. This species appears to have great seed yield potential, perhaps exceeding other species. A solution to the dormancy problem in C. viscosissima is undoubtedly forthcoming from selection programs and will greatly aid us in experimenting with this species. C. carthagenesis is not well adapted to cool climates; however, it is apparently well adapted to the warm climates of the southeast US. C. calophylla (n = 8), an uninvestigated species, may have an ideotype superior to C. carthagenesis and is worth investigating (Graham pers. commun.). Yield data on C. carthagenensis and C. calophylla from the southeast U.S. and other areas are badly needed to rank these species.
Cuphea germplasm resources have greatly increased over the last few years owing to collections made by the USDA-ARS and OSU. A recent USDA-ARS collection of 50 C. viscosissima populations made by W.R. Roath and M. Widrlechner (USDA-ARS, Ames, Iowa) is particularly noteworthy OSU and USDA-ARS germplasm resources include 2 C. lutea, 6 C. carthagenensis, 7 C. wrightii, 46 C. tolucana, 6 C. laminuligera, 8 C. leptopoda, and 42 C. viscosissima accessions tracing to distinct wild populations. There are about 30 C. lanceolata accessions. One traces to a wild population. The others are from European botanical garden collections and have uncertain histories.
C. lutea, C. calophylla, and C. carthagenensis germplasm resources are limited to two, two, and six populations, respectively, with no apparent within population genetic variation. These populations probably went through bottlenecks since they were collected prior to the development of a USDA germplasm maintenance program. Thus, there is a definite need for increased germplasm resources in these species. W.R. Roath, USDA-ARS, Ames, Iowa is planning another U.S. exploration for C. viscosissima and an exploration in Brazil in 1989. Numerous C. carthagenensis and C. calophylla populations should be found in Brazil (Graham pers. commun.).
The numerical abundance of accessions alone is not a useful measure of genetic variation in the Cuphea collection. There is, for example, tremendous within accession genetic variation in allogamous species and no or limited within accession genetic variation in autogamous species accessions collected before 1986. Some of these differences may be attributed to how these populations were preserved and multiplied; nevertheless, there are gross differences in total within species generic variation. Mating systems are often correlated with species gene pool variation. Allogamous species generally have greater total within species genetic variation than autogamous species regardless of how the variation is distributed. There is some evidence for this in Cuphea and abundant evidence in other species. In autogamous species we have observed no allozyme variation within accessions and only limited allozyme variation between accessions. We have, in contrast, observed extensive within and between accession allozyme variation in allogamous species.
Similar patterns of variation have been observed for economically important traits in pre-1986 Cuphea accessions. We have, for example, observed extensive within population variation for seed dormancy and oil percentage in allogamous species (two C. lanceolata populations and one C. laminuligera population) and no within population variation in autogamous species (two C. lutea populations and one C. viscosissima population). We expect to observe between population variation in autogamous species but have not had necessary germplasm resources.
Cuphea presents the greatest domestication challenge among the new industrial oilseed crops. Whether or not it is successfully commercialized hinges on eliminating seed dispersal. The economic rewards for doing so are obviously great.
We have been assessing the agronomic potential of several Apiaceae in cooperation with the USDA-ARS) at Ames, Iowa and Peoria, Illinois. Dill, coriander, anise (Pimpinella anisum L.), and fennel (Foeniculum vulgare L.) have been grown in experiments at Corvallis, Oregon and Ames. We chose these species for study for several reasons. First, they are commercially grown in Oregon for their essential oils or as seed crops. Second, there are extensive germplasm resources in several species, notably dill and coriander, and substantial within species genetic variation. Third, they are adapted to combine harvesting. Fourth, they require minimum irrigation and apparently are drought tolerant. Fifth, they are annuals. There are, however, annual and biennial fennels Several domesticated species were excluded because they are biennials, e.g., carrot (Daucus carota L.). Information on the agronomic performance of the Apiaceae is limited. We evaluated the yield of two dill and two coriander accessions and one anise accession in a preliminary yield trial in 1987 at Corvallis. Seed yields ranged from 670 to 1370 kg/ha. These yields are similar to those achieved in commercial dill seed production fields in Oregon. We adopted a seedling rate (4.5 kg/ha) and row spacing (0.75 m) (approximately 80 seeds/m) commonly used for dill seed production, but, after observing the experiment, concluded plant density was probably below optimum.
Seed oil percentages in the 1987 Corvallis experiment were exceptionally low. Dill and coriander seed oil percentages ranged from 8.5 to 10.5% and 12.6 to 13.4%, respectively. These percentages are about half of those previously reported for dill and coriander (Kleiman and Spencer 1982) and certainly are not competitive among oilseed crops. Data on 1988 experiments (approximately 50 accessions of dill, coriander, fennel, and anise were evaluated at Ames and Corvallis) are needed to determine whether or not this variation is representative of these species. Unfortunately, there is no knowledge about generic variation for fixed oil percentage traits in these species. Oil percentages in the range of 30 to 40% are undoubtedly needed for an economically viable oilseed crop but seem improbable in dill, coriander, and anise. We are uncertain about fennel since it was not included in the 1987 experiment. Kleiman and Spencer (1982) observed oil percentages in fennel similar to those in coriander.
Potential alternatives to the afore mentioned species are Bifora radians Bieb. (49.5% oil) and B. testiculata (L.) Spreng. (41.5% oil) (Kleiman and Spencer 1982). The agronomic potential of these species is unknown. Furthermore, we may observe, as for other species, lower oil percentages under cultivation.
There are no agronomic traits preventing commercial production of dill, coriander, or fennel as oilseed crops. Commercial seed production for the seed trade is already practiced. Seed shattering is a minor problem in dill and coriander but has been observed in crops allowed to stand for prolonged periods after seed maturation. Seed loss to shattering is minimized by sound harvest management.
Certain Apiaceae have immediate domestic production potential; however, their development as oilseed crops seems unlikely without high oil percentage cultivars and increased interest in petroselenic acid among industrial users of lauric and adipic acid.
Limnanthes is comprised of species with mating systems ranging from highly autogamous to highly, allogamous (Jain 1978, Kesseli and Jain 1985, Ritland and Jain 1981). The allogamous species are insect pollinated. Highly allogamous species, e.g., L. alba and L. douglasii, are characterized by abundant allozyme and economic and morphological trait variation, inbreeding depression and heterosis, high seed yields relative to autogamous species, and the requirement of insect pollination (Abuelgasim 1982; Brown et al. 1979; Jain 1978; Krebs and Jain 1985; Pierce and Jain 1977). Highly autogamous species (e.g., L. floccosa var. floccosa) have less allozyme and economic and morphological trait variation and lower seed yields than allogamous species, no inbreeding depression, and no insect pollinator requirement. On the one hand, allogamous species are preferred because their seed yields and genetic variation are substantially greater than those of autogamous species. On the other hand, autogamous species are preferred because they do not require insect pollination.
Honeybees have been used in commercial meadowfoam plantings. There has been speculation about reduced seeds yields in certain years caused by reduced bee activity during cool, wet weather. This speculation is based on field observations; however, year to year variation in seed yield and pollinator activity has not been documented. Honeybees are apparently unable to make honey from meadowfoam forage because of a lack of nectar, thus increasing production costs. Despite these problems there are no competitive autogamous species. L. alba and L. douglasii are logical candidates for domestication (Krebs and Jain 1985.)
Natural genetic variation for seed retention was discovered in L. alba by W. Calhoun and J. Crane at Oregon State University in 1972. Seed retention variation has apparently not been found in L. douglasii. Thus, L. alba has a definite advantage over L. douglasii even though L. douglasii seed yields have been greater in certain environments (Krebs and Jain 1985).
There is substantial genetic variation for quantitative traits in L. alba (Abuelgasim 1982, Jain and Abuelgasim 1981, Krebs and Jain 1985, Pierce and Jain 1977) but it has not been adequately exploited. There are several reasons for this situation. First, there is no USDA program for meadowfoam germplasm collection, evaluation, and enhancement. Second, efficient breeding methods have not been continuously, applied to the improvement of L. alba. Third, the selection program at Oregon has been restricted to a narrow germplasm base, mainly an L. alba population derived from a few individual plant selections in PI283703 and PI283704 and a few interspecific hybrid crosses between L. alba and L. floccosa or L. gracilis. Fourth, the heterotic potential of L. alba has not been exploited.
The USDA L. alba germplasm collection at Pullman, Washington is comprised of 18 accessions tracing to wild populations. Data on within and between accession (population) variation are not available, at least there are no published data. Additional L. alba accessions are stored in the collection of S.K. Jain at U.C. Davis. Data on these accessions are available (Pierce and Jain 1978, Krebs and Jain 1984). There is a need to organize the germplasm resources of L. alba and other species, preserve them in a national collection, evaluate existing populations, and collect and evaluate additional populations.
Significant increases in meadowfoam seed yields are needed over the next several years to commercialize meadowfoam. An efficient route to achieving needed increases is a breeding program based on recurrent S1 family selection (Wright 1980) for increased seed oil yield. The rate of increase, besides being method dependent, is dependent on the magnitude of heritable variation in base populations, selection intensity, and selection criteria (Baker 1984).
Improved meadowfoam cultivars originating in the Oregon program apparently trace to public (USDA) accessions PI283703 and PI283704. Exposure of "selected" populations to populations besides those originating from these PIs may have occurred during their development. Thus, new variation may, have been inadvertently introgressed into these populations since isolation was rarely used in their development. The record is not very clear on this matter. An increase in generic variation in base populations, beyond the variation currently being exploited, is needed to exploit the yield potential of meadowfoam. However, new, variation must be introgressed without seriously compromising population mean seed yields (Goodman 1985). An efficient way of doing this is to ensure that elite population gene frequencies are greater than exotic population gene frequencies in populations developed by intermating elite and 'exotic' populations (Dudley 1982, Bridges and Gardner 1987). One method of doing this is to develop backcross populations using elite populations as recurrent parents. This is not practical in meadowfoam since there is no way to emasculate large numbers of plants. An alternative is to synthesize and intermate new populations using a greater proportion of elite germplasm. At least one generation of intermating is useful beyond the initial hybridization generation.
Even greater increases in meadowfoam seed yields may be achieved if breeding efforts are focused on exploiting the heterotic potential of L. alba. Heterosis has not been exploited to this pointquite the opposite. Jolliff et al. (1984) have striven to increase the level of self-pollination in L. alba populations by developing interspecific hybrids between L. alba and L. floccosa and selecting for autofertility and the L. alba phenotype. Their purpose has been to eliminate the need for insect pollination; however, increased self-pollination in L. alba has detrimental effects on quantitative traits, e.g., seed yield and fecundity (Jain 1978). It is impossible to determine whether or not self-pollination has been increased in populations selected for increased autofertility since outcrossing rates have not been estimated (Jolliff et al. 1984). It is questionable at best to pursue a strategy, for increasing self-pollination in a highly allogamous species subject to inbreeding depression when the main stumbling block to commercialization is seed yield. Seed yield and self-pollination rate are strongly negatively, correlated in L. alba (Jain 1978), so they cannot be optimally simultaneously selected.
Heterosis is typically exploited through the use of hybrid (intraspecific) and synthetic cultivars. Genetic pollen control mechanisms for hybrid seed production, e.g., cytoplasmic-genic male-sterility, have not been discovered in L. alba, so there is no possibility for hybrid seed production in this species short of using gametocides to sterilize female lines. A suitable mechanism for exploiting heterosis in meadowfoam is synthetic cultivars. Their development, however, requires greater time and financial resources than needed for the development of open-pollinated cultivars.
Meadowfoam is a potentially useful new oilseed crop but suffers because there are no established markets for its seed oils. Without markets this crop will remain a novelty.
Stokes aster is a source of epoxy fatty acids. Campbell (1981) evaluated the Stokes aster germplasm collection (20 accessions) for various traits. Population mean seed oil percentages ranged from 27.0 to 44.0% (Campbell 1981). Vernolic acid, the major epoxy fatty acid in Stokes aster, percentages ranged from 63.9 to 78.8%. Furthermore, seed yield potential has been estimated at 2000 kg/ha.
Epoxy fatty acids are presently obtained by processing linseed and soybean oils because there are no direct commercial sources. Stokes aster, however, is a potential commercial source of epoxy fatty acids. It is remarkable that this crop has not been exploited. It has no serious competition among new temperate oilseed crops. Vernonia galamensis L., an epoxy fatty acid oilseed crop, is not adapted to the U.S. Vernonia anthelminia Willd. is adapted to the U.S. but has a serious seed retention problem.
Stokes aster is a perennial and apparently has few agronomic problems. Stand establishment is difficult and slow but no selection work has been done to increase seedling vigor and reduce seed dormancy (Campbell 1981). It is difficult to determine whether or not perenniality is an advantage or disadvantage. I perceive it as an advantage since perennials should have a significant role in sustainable farming systems. Stokes aster is indigenous to the U.S. and has been extensively collected. Approximately 20 accession reside in the USDA germplasm collection. There apparently is substantial genetic variation in these populations. There is, for example, extensive variation in seed retention. Campbell (1981) has selected populations with closed bracts giving seed retention.
The market potential for seed oils rich in epoxy fatty acids is between 45,000 and 90,000 t/yr (Campbell 1981, Princen 1983). Stokes aster ought to be able to capture at least part of this market and is a crop waiting to be exploited. Sustained breeding work and industrial interest are needed to get Stokes aster commercialized.
Money plant and meadowfoam have identical market development problems. Basically, there are no established industrial markets for their seed oils. There apparently are no serious agronomic problems with Lunaria, e.g., seed shattering is not a problem, but the development of this crop is doubtful without a significant change in the present market outlook.