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REGISTRATIONS OF GERMPLASMS

Registration of TTU-LRC Castor Germplasm with Reduced Levels of Ricin and RCA₁₂₀

^a Dep. of Plant and Soil Science, Texas Tech Univ., Lubbock, TX 79409-2122
^b Agribusiness, Agronomy, Horticulture, and Range Management, Tarleton State Univ., Stephenville, TX 76402
^c Department of Microbiology and Immunology, Texas Tech Univ. Health Science Center, Lubbock, TX 79430
^d Cancer Immunology Center and Department of Microbiology, Univ. of Texas Southwestern Medical Center, Dallas, TX 75235-8576

^* Corresponding author (dick.auld{at}ttu.edu)

An open-pollinated germplasm population of castor (Ricinus communis L.) TTU-LRC (Reg. no. GP-3, PI 631156) was developed at Texas Tech University and released in 2002. The eight F₆ parental lines of TTU-LRC were selected for reduced levels of two toxins found in castor seeds, ricin and R. communis agglutinin (RCA₁₂₀), as well as dwarf-internode growth habit. The toxins found in castor meal residue after oil extraction must be denatured before it can be fed to livestock (Roetheli et al., 1991, p. 36). Ricin is extremely toxic and may have potential for use in chemical warfare (Cope et al., 1945), as well as cancer immunotherapy (Ghetie and Vitetta, 1994; Vitetta and Thorpe, 1991). The TTU-LRC germplasm population was released to provide germplasm for breeding programs developing cultivars for mechanized harvesting.

TTU-LRC is an open-pollinated population obtained by randomly intercrossing eight F₆ parental lines. Three of the F₆ lines originated from crosses made in 1994 between PI 257654 and ‘Hale’, while five of the F₆ lines originated from a cross between PI 258368 and Hale. Hale is a high yielding, dwarf-internode cultivar released by USDA-ARS and Texas A&M University in 1961 (Brigham, 1970). Both PI 257654 and PI 258368 were developed in the former Soviet Union where they were selected for low levels of seed toxins (Moshkin, 1986, p. 81–92). Open-pollinated F_3, F₄, and F₅ seeds of these crosses were screened for reduced levels of ricin and RCA₁₂₀ by means of a radial immunodiffusion (RID) assay (Pinkerton et al., 1999). Plants were also simultaneously selected for dwarf-internode growth habit.

Approximately 50 F₇ plants from each of the eight F₆ parental lines were randomly intercrossed in an isolated field nursery during the 2000 growing season at Lubbock, TX. Approximately 40 plants, which did not exhibit dwarf-internode growth habit, were removed before pollination. Phenotypic analyses conducted on a sample of 118 F₆ plants showed that plant height ranged from 33 to 119 cm. Limited cross-pollination had occurred during selfing as indicated by traits not present in the base population. Spineless capsules occurred in less than 10% of plants and red stems or leaves occurred in less then 5% of the plants. The RID assay was used to determine the combined ricin and RCA₁₂₀ contents of 30 open-pollinated seeds harvested from the 2000 crossing block. These seeds ranged from 0.10 to 5.60 mg of ricin and RCA₁₂₀ g^-1 and averaged 1.86 mg ricin and RCA₁₂₀ g^-1. This compares to an average 12.2 mg ricin and RCA₁₂₀ g^-1 in the cultivar Hale in an earlier study (Pinkerton et al., 1999). Seeds of PI 257654 and PI 258368 averaged 1.5 and 2.9 mg ricin and RCA₁₂₀ g^-1 seed in this study, respectively.

This heterogenous population should provide a source of valuable breeding lines which combine reduced levels of toxins with the dwarf-internode growth habit (0.3–1.25 m) necessary for mechanized harvest. The Plant and Soil Science Department at Texas Tech University will maintain seed stocks. Approximately 100 seeds will be made available to researchers on request to the corresponding author. Appropriate recognition should be made if this germplasm contributes to the development of new breeding lines or cultivars. U.S. Plant Variety Protection for TTU-LRC will not be applied for.

ACKNOWLEDGMENTS

Funding for this research was provided by the Texas Tech University Plant Science Research Item, by the USDA-CSRS (CSREES), by the Advanced Technology Program- Texas Higher Education Coordination Board, and by the USDA-Initiative for Future Agriculture and Food Systems (IFAFS). Raymond Brigham (TAMU-TAES, Lubbock, TX), Harry Parker (TTU), and Brenda Lauterbach (TAMU-TAES, Lubbock, TX) contributed to the development of this germplasm population.

NOTES

This is contribution number T- 4-522 of the College of Agricultural Science and Natural Resources, Texas Tech University. Registration by CSSA.

Accepted for publication September 30, 2002.

REFERENCES

• Brigham, R.D. 1970. Registration of castor variety Hale (Reg. No. 3). Crop Sci. 10:457.[Free Full Text]
• Cope, A.C., J. Dee, R.K. Cannan, B. Renshaw, and S. Moore. 1945. Ricin. Chapter 12. p. 179–203. In Chemical warfare agents and related chemical problems- Part I. Summary Technical Report, Div. 9, National Defense Research Committee. (Declassified Secret)
• Ghetie, V., and E. Vitetta. 1994. Immunotoxins in the therapy of cancer: From bench to clinic. Pharm. Ther. 64:209–234.
• Moshkin, V.A. (ed.) 1986. Castor. Amerind Publishing Co. PVT Ltd. New Delhi.
• Pinkerton, S.D., R.D. Rolfe, D.L. Auld, V. Ghetie, and B.F. Lauterback. 1999. Selection of castor with divergent concentrations of ricin and Ricinus communis agglutinin. Crop Sci. 39:353–357.[Abstract/Free Full Text]
• Roetheli, J.C., L.K. Glaser, and R.D. Brigham. 1991. Castor: Assessing the feasibility of U.S. production. USDA-CSRS, Office of Agricultural Materials. Washington, DC.
• Vitetta, E.S., and P.E. Thorpe. 1991. Immunotoxins containing ricin or it's A chain. Cell Biol. 2:42–58.

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