Location: Northwest Irrigation and Soils Research
Project Number: 2054-21220-005-001-S
Project Type: Non-Assistance Cooperative Agreement
Start Date: May 1, 2019
End Date: Apr 30, 2022
The objective is to develop strain specific infectious clones of Beet Curly Top Virus (BCTV). Developing infectious clones of Beet curly top virus (BCTV) strains found in western U.S. will benefit breeding for curly top resistance in sugar beet by allowing strain specific resistance to be identified. Maintaining single virus strains in beet leafhopper populations has proven to be problematic. Thus, infectious clones are the only effective means to screen for strain specific resistance to BCTV.
ARS in Kimberly, Idaho has provided DNA from Idaho for the University of Idaho (UI) cooperator to develop infectious clones of BCTV strains. There is a need for additional clones including the Kim1 strain in Idaho and strains representative of different genetic clades from other states. The ARS sugar beet research group in Idaho will provide the DNA necessary for the clones to be developed by the UI cooperator for these other areas. The infectious clone design will follow the successful design strategy used by the UI cooperator to develop clones for the strains of BCTV. Specifically, cloned sequences for Kim1 and other strains of interest will be used for re-cloning into a binary vector between a 35S-promoter and a NosT terminator. A. tumefaciens strains C58 or LB4404 transformed with these clones will be grown in liquid medium prior to infiltration into young sugar beet plants to test for curly top infectivity and resistance. The initial infectivity tests will be conducted in a susceptible sugar beet variety like Monohikari, but once infectivity is confirmed, all clones will be tested on the entire range of sugar beet lines submitted for screening. At 3-weeks post inoculation with a clone, curly top infection symptoms will become visually evident. The visual symptoms will be confirmed by two laboratory methods: enzyme-linked immunosorbent assay (ELISA) and polymerase chain reaction (PCR) using strain specific primers. Visual scoring for curly top symptoms will follow a system used by the ARS sugar beet breeding program in Kimberly for resistance screening using leafhopper transmission. Similar check varieties will be used for susceptible and resistant controls and will be provided by the ARS group in Kimberly.