Submitted to: Field Crops Research
Publication Type: Peer reviewed journal
Publication Acceptance Date: 10/27/2008
Publication Date: 1/23/2009
Citation: Gilbert, R.A., Glynn, N.C., Comstock, J.C., Davis, M.J. Agronomic performance and genetic characterization of sugarcane transformed for resistance to sugarcane yellow leaf virus. Field Crops Res. 111:39-46 Interpretive Summary: Control of the widespread and economically important disease, sugarcane yellow leaf is best achieved through varietal resistance; however, resistance to causal agent Sugar Cane Yellow Leaf Virus (SCYLV) is limited in the parental germplasm. Genetic transformation of crops with viral coat protein coding sequences modified to render them inactive has proved to be a successful strategy in the development of virus resistant varieties. Therefore, the coat protein sequences were inserted into an existing commercial sugarcane variety to provide resistance to SCYLV. Since the tissue culture techniques may cause genetic alterations that negatively impact yield, the transformed clones were evaluated for their agronomic performance. The transformed clones were resistant to the virus but had lower yields than the non-transformed donor clone. The implications of these results are that these transformed clones can not be used commercially but may be of use in conventional breeding to incorporate the coat protein sequences into high yielding genotypes with resistance to SCYLV.
Technical Abstract: The Sugar Cane Yellow Leaf Virus (SCYLV) is widespread in Florida, and SCYLV resistance in the Canal Point (CP) sugarcane population is limited. The objectives of this study were to 1) evaluate the agronomic performance of two transgenic lines transformed for SCYLV resistance (6-1, 6-2) compared to parental cultivar CP 92-1666, 2) determine level of SCYLV resistance in the transgenic lines, and 3) characterize genetic differences in the transgenic lines compared to CP 92-1666. Sucrose yields of CP 92-1666 were 6.5 – 8.7 tons sucrose ha-1 yr-1 more than either the transgenic lines, or the tissue culture (C-1) or NPTII marker gene (20-1) controls,. However, SCYLV infection rates in transgenic lines were only 0-5%, compared to 98% in CP 92-1666. Selectable marker gene NPTII was stably expressed in all co-transformed lines. SSR genotyping showed 35 additional fragments present and 25 existing fragments absent among 6-1, 6-2, C-1 and 20-1 compared to CP 92-1666. The four regenerated clones showed a greater genetic distance from the donor clone CP 92-1666 (mean GD 0.4) than to one another (mean GD 0.03). This study reports the first field evaluation of sugarcane transformed for SCYLV resistance, and the first report of variations in microsatellite repeat number associated with regeneration from embryogenic callus. Transgenic lines 6-1 and 6-2 are being used as parents in crosses designed to combine SCYLV resistance with agronomic characteristics of high-yielding germplasm.