U. S. Horticultural Research Laboratory 2001 South Rock Road Fort Pierce, FL 34945 Telephone: (561) 462-5806 Fax: (561) 462-5986 Email: RNiedz@ushrl.ars.usda.gov

Current Research Projects

Dr. Niedz is a Research Geneticist conducting research on the development and application of cellular and molecular breeding methods for citrus scion and rootstock variety improvement. These methods are used to transfer, known sources of resistance to diseases, pests, and environmental stresses, to improve the horticultural quality of the fruit and tree, and to develop populations suitable for the genetic characterization of these traits in citrus. Specific objectives include methods to develop seedless citrus, methods to control tree size for efficient production and harvesting, and methods to regenerate trees from high value cell types, tissues, or organs (e.g., immature pollen grains) for citrus genomic studies and mutant isolation.

	Globular stage somatic embryos of 'Hamlin' sweet orange.		Torpedo stage somatic embryo of 'Hamlin' sweet orange.		Germination of 'Hamlin' sweet orange somatic embryo.

Selected Publications

Niedz, R.P. Culturing embryogenic protoplasts of 'Hamlin' sweet orange in calcium alginate beads. Plant Cell, Tissue and Organ Culture 34:19-25. 1993.

Vu, J.C.V., Niedz, R.P., and Yelenosky, G. Glycerol stimulation of chlorophyll synthesis, embryogenesis, and carboxylation and sucrose metabolism enzymes in nucellar callus of 'Hamlin' sweet orange. Plant Cell, Tissue and Organ Culture 33:75-80. 1993.

Osswald, W.F., Shapiro, J.P., McDonald, R.E., Niedz, R.P. and Mayer, R.T. Some citrus chitinases also possess chitosanase activities. Experientia 49:888-892. 1993.

Niedz, R.P. Growth of embryogenic sweet orange callus on media varying in the ratio of nitrate to ammonium nitrogen. Plant Cell, Tissue and Organ Culture 39:1-5. 1994.

Doostdar, H., Shapiro, J.P., Niedz, R., Burke, M.D., McCollum, T.G., McDonald, R.E., and Mayer, R.T. A cytochrome P450 mediated naringenin 3'-hydroxylase from sweet orange cell cultures. Plant Cell Physiol. 36:69-77. 1995.

Bausher, M.G., Nairn, J.C., Niedz, R.P., Hearn, C.J., and Yelenosky, G. Purification and N-terminal sequence of the major leaf protein (trifoliatin) from trifoliate orange. Plant Science 109:145-152. 1995.

Vu, J.C., Niedz, R.P., and Yelenosky, G. Activities of sucrose-metabolizing enzymes in glycerol-grown suspension cultures of 'Hamlin' orange (Citrus sinensis L. Osbeck). Environmental and Experimental Botany 35:455-463. 1995.

Niedz, R.P., Sussman, M.R., and Satterlee, J.S. Green fluorescent protein: an in vivo reporter of plant gene expression. Plant Cell Reports 14:403-406. 1995.

Mayer, R.T., McCollum, T.G., Niedz, R.P., Hearn, C.J., McDonald, R.T., Berdis, E., and Doostdar, H. Purification and characterization of seven basic endochitinases isolated from cell cultures of Citrus sinensis (L.). Planta 250(3):289-295. 1996.

Nairn, C.J., Niedz, R.P., Hearn, C.J., Mayer, R.T., and Yelenosky, G. cDNA cloning and expression of a class II acidic chitinase from sweet orange. Biochim. Biophys. Acta. In Press. 1997.

Shapiro, J.P., Hall, D.G., and Niedz, R.P. Mortality of larval root weevil Diaprepes abbreviatus (Coleoptera: Curculionidae) in simulated flooding. Florida Entomologist 80:277-285, 1997.

Niedz, R.P., Moshonas, M.G., Peterson, B., Shapiro, J.P., and P.E. Shaw. Analysis of sweet orange (Citrus sinensis (L.) Osbeck) callus cultures for volatile compounds by gas chromatography with mass selective detector. Plant Cell, Tissue and Organ Culture 51:181-185, 1997.

Niedz, R.P. Isothiazolone biocides to control microbial and fungal contaminants in plant tissue cultures. HortTechnology 8:598-601, 1998.

Bausher, M. and Niedz, R. A discussion of in vitro contamination control of explants from greenhouse and field grown trees. Proceedings Florida State Horticultural Society. 1998. 111:260-263.

Möder, W., Bunk, A., Albrecht, A., Doostdar, H., Niedz, R.P., McDonald, R.E., Mayer, R.T., and Osswald, W.F. Characterization of acidic chitinases from culture medium of sweet orange callus tissue. Journal of Plant Physiology 154:296-301, 1999.

McCollum, T.G., Doostdar, H., Niedz, R.P., Mayer, R.T., Burkhart, M., and McDonald, R.E. Biochemical, molecular genetic, and immunological characterization of a ß-1,3-endoglucanase from 'Valencia' orange callus. J. Plant Physiology 155:16-23, 1999.

Niedz, R.P., McKendree, W.L., and Robert G. Shatters, Jr. Electroporation of sweet orange protoplasts and regeneration of transgenic plants. (Plant Cell Reports, In Review)

McKendree, W.L., Chaparro, J.X., and Niedz, R.P. Copia-like retrotransposon families of Citrus. (Plant Molecular Biology, In Review)

Last modified: 2/12/2001.   Send comments or questions to RNiedz@ushrl.ars.usda.gov