Commercial production of castor existed in the central United States as early as 1850. By 1959, Texas was the leading producer of castor with over 30,000 ha of castor being grown in the late 1960s. During this period, over 23 crushing mills reportedly were operating in Texas (Brigham, 1989). U.S. castor production ceased in the early 1970s due to: (1) contract negotiation problems between oil buyers and the farm cooperative involved in crushing castor, (2) low world prices for castor oil, (3) competition between castor and other crops for which high prices were being paid, and (4) discontinuation of government price supports in 1972.
The seed, leaves, and stem of castor are poisonous to humans and livestock if consumed (Zimmerman et al. 1958). Ingestion of even one seed can be fatal to humans (Naughton 1979). Ricin, a very lethal protein, is the major toxic component. Ricinine, a poisonous alkaloid, exists at very low levels and presents little problem (Horton and Williams 1989). In addition, castor contains an allergin (known as CB-1A) which can cause an allergic reaction in humans (Roetheli et al. 1991a).
The United States is totally dependent upon imports to meet the industry and defense needs for castor oil. A total dependence on imported castor oil places the United States in a vulnerable position should the supply be interrupted because of world events. A domestic crop would provide a stable source of supply. To replace imports, the United States would need about 45,000 ha of castor to supply domestic users (Roetheli et al. 1991b). Considerable importance must also be given to potential exports of U.S.-produced castor oil to France, nations of former USSR, Germany, and UK.
Since seeds of Lesquerella fendleri (L.) contain oil that is similar to castor oil, it is a potential replacement for castor (Roetheli et al. 1991a). Under the new crops program of Virginia State University, research was conducted during 1992, 1993, and 1994 to evaluate the potential of Lesquerella fendleri (L.) under Virginia conditions and to develop it as a domestic source of hydroxy fatty acids and as a replacement for castor. Field and greenhouse experiments to evaluate lesquerella germplasm, planting times, and fertilizer rates, indicated that lesquerella production under Virginia conditions may not be feasible, largely due to lack of adequate germination/stand establishment and biomass production.
Based on these negative observations, it was decided, in 1994, to initiate research with castor. The objective of this research was to determine feasibility of castor production under Virginia conditions and to evaluate castor germplasm for agronomic and oil characteristics and to lay the foundation for a castor breeding program.
Five hills (3 to 5 seeds/hill) of each accession were planted on May 13, 1994 in rows spaced 1.5 m apart. Upon germination, each hill was thinned to one plant/hill. The distance between plants was 60 cm. The seedheads (racemes) were hand-harvested from each plant twice (Sept. 28 and Dec. 6, 1994). No yield data were available for accessions PI250026 and PI250881 due to extremely sever shattering. The capsules were shelled by hand.
Plant height (cm) was determined at final harvest. Seed yield per plant was converted to tonnes/ha. Oil content in the open-pollinated seeds and percentage of ricinoleic acid in the oil were determined by standard chemical techniques. The ricin was extracted from castor seeds using the method of Lis and Sharon (1972). The agglutinating ability of ricin, determined by using the quantitative method described by Turner and Liener (1975), was used to calculate the ricin content in mg/g of meal.
The mean seed yield (calculated by using single plant yield) of 70 accessions was 1 t/ha with a range from 0.1 to 2.6 t/ha. 'Hale' yielded 1.4 and 'Lynn' yielded 1 t/ha. The highest yielding accession, PI257457, from South Africa, had a seed yield of 2.6 t/ha.
Significant positive correlation existed between yield and 100-seed weight and yield and oil content (Table 2). The content of ricinoleic acid had a negative correlation with yield. A significant negative correlation (-0.30) existed between seed weight and ricin content. The existence of variation for ricin and the lack of a significant relationship with yield, oil content and ricinoleic acid indicated that a breeding program could be successfully undertaken to reduce the ricin content, thus, reducing or eliminating the problems associated with this toxic compound.
Our results indicate that commercial castor production in Virginia is feasible. Furthermore, the results suggest that a high potential of success if breeding efforts are undertaken to develop improved cultivars of castor combing high yields of seed with high oil content and quality.
|Entry||Country||Yield (t/ha)||Height (cm)||100-seed wt(g)||Oil (%)||RAcidz (%)||Ricin (mg/g)|
|Correlation coefficients (r)|
|Character||100-seed weight||Plant height||Oil content||Ricinoleic acid content||Ricin content|
|Ricinoleic acid content||0.10|