Curly top of sugarbeet is caused by Beet severe curly top
virus (BSCTV) or closely related curtovirus species which
are vectored by the beet leafhopper (Circulifer tenellus).
Beta corolliflora, shown in 1969 to impart a very high level
of curly top resistance to sugarbeet into the BC2 generation,
is a wild relative of cultivated sugarbeet that has not
been utilized in breeding programs. The nature of curly top
resistance from B. corolliflora seems to be reduced symptoms
and resistance to viral accumulation. Field screening
of 14 B. corolliflora accessions for resistance to curly top
followed by PCR detection of BSCTV did not identify any
accessions with phenotypic symptoms of curly top and 9
accessions did not have detectable virus. Clip cage inoculations
followed by PCR detection of BSCTV and of related
species, Beet mild curly top and Beet curly top viruses, were
difficult to interpret due to small sample size but indicated
that accessions BETA 408, BETA 414, BETA 528,
BETA 690, and BETA 805, from Genebank Gatersleben,
Foundation Liebniz Institute of Plant Genetics and Crop
Plant Research, Gatersleben, Germany had no visible curly
top symptoms or evidence of virus accumulation. Results
of a preference test showed that beet leafhoppers did not
have a strong aversion to B. corolliflora and likely would
have at least sampled the plants in the field. Therefore,
field screening for resistance to curly top, at least in the
early generations of an introgression program, should be
successful
