Submitted to: Field Crops Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/26/2010
Publication Date: 9/28/2010
Citation: Glynn, N.C., Gilbert, R.A., Comstock, J.C., Davis, M.J. 2010. Transmission of a Sugarcane Yellow Leaf Virus transgene to sexual progeny and screening by kanamycin inoculation. Field Crops Res. 119:308-313.
Interpretive Summary: Sugarcane (a complex Saccharum hybrid) yellow leaf caused by the sugarcane yellow leaf virus (SCYLV) is endemic in many sugarcane growing regions. Inadequate sources of SCYLV resistance limit conventional breeding for resistance. Transgenic technology offers the potential for improving SCYLV resistance, however, agronomic performance may be negatively impacted in transformed cultivars. Such problems could be overcome or reduced by transgene transfer through conventional crosses. However, the identification of progeny that have inherited the transgene usually requires DNA analysis methods which are costly when applied to a large number of progeny. Two transgenic clones were evaluated for their use in conventional crosses for transferring a SCYLV transgene to progeny. The clones showed variable breeding performances but both produced viable seed. Analysis of seedlings produced from these clones showed approximately 50% of progeny inherited both the SCYLV transgene and a selectable marker gene. These results demonstrate that despite negative agronomic performance associated with these transgenic clones, they possess useful potential for transferring the SCYLV transgene to high yielding sugarcane genotypes. Plants were grown at the University of Florida, Belle Grade Station.
Technical Abstract: The objectives of this work were i) to evaluate the utility in conventional breeding of sugarcane genotypes 6-1 and 6-2 previously transformed with the nptII selectable marker and an untranslatable SCYLV coat protein (U-SCYLV-CP) sequence, ii) examine the inheritance of these inserts and the potential of kanamycin sensitivity as a selectable marker for the U-SCYLV-CP insert in the derived progeny. 6-1 and 6-2 were used as parents in 12 crosses over three years, germination rates of the resulting true seed were comparable with those for the untransformed parent, CP 92-1666, and with other crosses made in the same seasons. Inheritance and function of the nptII insert was tested in 215 seedlings from three crosses through the application of a solution containing 3.0 g L-1 kanamycin. PCR analysis confirmed the presence of the nptII insert transgene in 172 (95.6%) of the 180 kanamycin resistant progeny. Both transgenes were present in 107 (49.8%) of the kanamycin resistant progeny. Segregation analysis of the data suggests that the nptII insert is integrated at two linked loci in 6-1 and 6-2 one of which is functional and linked to the U-SCYLC-CP integration loci. These results demonstrate the utility of 6-1 and 6-2 for transferring the U-SCYLV-CP insert to additional sugarcane genotypes and the effectiveness of kanamycin application for screening sexual progeny and will be useful in guiding strategies to improve resistance to the SCYLV through transgenics.