Agronomic Evaluation of Sugarcane Lines Transformed for Resistance to Sugarcane mosaic virus Strain E

zki (1993) noted that genetic engineering in sugarcane would be a useful tool for reversing single flaws, such Genetic transformation of sugarcane (Saccharum spp.) holds promas disease susceptibility, in commercial cultivars. Sugarise for increasing yields and disease resistance. However, the tissue cane may benefit from genetic transformation because its culture and transformation process may produce undesirable field characteristics in transgenic sugarcane. The primary objective of this high ploidy level makes traditional breeding programs study was to evaluate variability in agronomic characteristics and difficult, while vegetative propagation of sugarcane allows field disease resistance of sugarcane transformed for resistance to for relatively stable transfer and multiplication of transSugarcane mosaic virus (SCMV) strain E. One hundred plants derived genic materials (Gallo-Meagher and Irvine, 1996). from cultivars CP 84-1198 (n 82) and CP 80-1827 (n 18), consisting Birch (1996) predicted that new gene technologies of independent virus resistant lines VR 1 (n 14), VR 4 (n 24), would reshape the sugar industry, yet obstacles to their VR 14 (n 4), and VR 18 (n 58) were evaluated in Exp. 1. implementation remain. For example, somaclonal variaTransgenics derived from CP 84-1198 had significantly greater tonnes tion caused by tissue culture procedures may produce of sucrose per hectare (TSH) and significantly lower SCMV disease undesirable field characteristics in genetically transincidence than those from CP 80-1827 in the plant-cane (PC), firstformed sugarcane that are not readily identifiable in the ratoon (1R), and second-ratoon (2R) crops. Plants from the VR 18 line had significantly greater economic indices and lower SCMV disease laboratory or greenhouse (Lourens and Martin, 1987; incidence than the VR 4 line in all three crops. Phenotypic variation Burner and Grisham, 1995; Oropeza and De Garcia, 1996; was high in Exp. 1, with tonnes of cane per hectare (TCH) ranging Sreenivasan and Jalaja, 1998; Arencibia et al., 1999). from 26 to 211 and TSH from 3.2 to 28.9 in the PC crop. Agronomic Burner and Grisham (1995) report significant somatrait variation decreased with increased selection pressure in Exp. 2, clonal variation in CP 74-383 sugarcane subjected to evaluating 30 VR 18 lines, with TCH ranging from 70 to 149 and TSH different propagation procedures. Normal variants infrom 8.5 to 19.0 in PC. The large variability in yield characteristics creased from the PC to 1R crops, but still totaled 22% and disease resistance encountered in this study demonstrates the of all plants. Lourens and Martin (1987) reported sonecessity of thorough field evaluation of transgenic sugarcane while maclonal variation in two sugarcane cultivars, CP 65-357 selecting genetically stable and agronomically acceptable material for and CP 72-356. The frequency of variants and suitability commercial use. of tissue culture treatments varied between cultivars, and they recommended that the effects of tissue culture on sugarcane be examined on a cultivar by cultivar basis. S mosaic virus has recently been increasing The increased genetic variability associated with soin frequency and extent in the Everglades Agriculmaclonal variation may produce beneficial characteristural Area of Florida (Comstock et al., 2000). Sugarcane tics as well as deleterious ones. Larkin and Scowcroft mosaic virus had devastating effects on the nascent sug(1981) identified genetic variability generated by tissue arcane industry in Florida in the 1920s (Bourne, 1972). culture as a potential source for plant improvement. Given the potential damage of SCMV to the $1-billion They noted that somaclonal variation in sugarcane was dollar Florida sugarcane industry, there is concern about easily obtained and affected important yield characteristhe epidemic potential of this disease. tics. Although somaclonal variation may be used to add Genetic transformation combined with field selection desired attributes (e.g., disease resistance) to sugarcane, may increase sugarcane yields and resistance to diseases they cautioned that stringent field testing was necessary such as SCMV (Birch, 1996). Previously, genetic transto determine the full extent and effect of genetic changes formation has been used to transfer herbicide resistance in putatively beneficial somaclones. Liu (1990) reported (Gallo-Meagher and Irvine, 1996; Falco et al., 2000; agronomically useful sugarcane mutants obtained through Leibbrandt and Snyman, 2003) and insect resistance tissue culture-induced somaclonal variation with greater (Arencibia et al., 1999) into sugarcane. Birch and Maretstalk number, stem length, and sucrose content than the donor plants, and Leal et al. (1996) used somaclonal R.A. Gilbert, Univ. of Florida, EREC, 3200 E. Palm Beach Rd., Belle variation as a source of eyespot disease resistance in sugarGlade, FL 33430; M. Gallo-Meagher, Univ. of Florida, Agronomy cane. Agronomic evaluation of transgene expression Dep., Plant Molecular and Cellular Biology Program, and Genetics changed with tiller generation in tall fescue (Bettany et Institute, P.O. Box 110300, Gainesville, FL 32611; J.C. Comstock and J.D. Miller, USDA-ARS, Sugarcane Field Station, 12990 U.S. Hwy. al., 1998). The authors suggested that selection for the 441, Canal Point, FL 33438; M. Jain and A. Abouzid, Univ. of Florida, active state of the transgene over several tiller generaAgronomy Dep., P.O. Box 110300, Gainesville, FL 32611. Received tions may assist in stabilizing gene expression, an ap30 Dec. 2004. *Corresponding author ([email protected]). Abbreviations: 1R, first ratoon; 2R, second ratoon; CP, Canal Point; Published in Crop Sci. 45:2060–2067 (2005). Crop Breeding, Genetics & Cytology DSI, disease severity index; EREC, Everglades Research and Education Center; KST, kilograms sucrose tonne 1; PC, plant cane; SCMV, doi:10.2135/cropsci2004.0771 © Crop Science Society of America Sugarcane mosaic virus; TCH, tonnes cane ha 1; TSH, tonnes sucrose ha 1; VR, virus resistant. 677 S. Segoe Rd., Madison, WI 53711 USA 2060 Published online August 26, 2005