Plant Genome I Conference
Town & Country Conference Center, San Diego, CA, November, 1992.
PG-I: 94pg1
MOLECULAR STUDIES OF Ac INDUCED CHROMOSOME BREAKAGE IN TOMATO
Chandler, J., Carriero, F., Blaker, N., Peterson, P., and
Yoder, J.I. Department of Vegetable Crops, University of
Caldomia-Davis
Xa-1 is a semidominant mutation which, when in the
heterozygous condition, produces bright yellow plants.
Transgenic tomato plants, bearing the maize transposable element
Ac, show somatic sectoring at the Xa-1 locus. Cytological and
genetic data support a model of Ac mediated chromosome breakage
followed by a breakage-fusion-bridge cycle to explain the
sectoring. Molecular markers flanking the Xa-1 locus are being
obtained for use in studying the sectoring mechanism. We have
identified 8 RFLP markers flanking the Xa-1 locus after screening
22 chromosome 10 specific probes obtained from Dr. S. Tanksley.
Polymorphisms are identified at a frequency of 3% per probe
enzyme combination. The 8 RFLP markers have been mapped in
relation to Xa-1 in a segregating intraspecific F2 population.
These markers are now being used in analysis of the sectoring.
Preliminary evidence supports the breakage-fusion-bridge cycle
model. In addition, RAPD markers flanking Xa-1 have been
identified. The bulked segregant analysis method was used to
screen the green (+/+) versus the yellow (Xa-il+) plants. No
polymorphisms were detected using 200 different primers and
screening approximately 1400 bands. To increase polymorphism
detection, we have utilized a segregating backcross population
prepared between Xa-1 and L. pennellii. In this case, 7
polymorphisms were detected using 320 primer and screening
approximately 1600 bands. The frequency of polymorphic bands is
0.44%. Five of the 7 polymorphic bands have been mapped in
relation to Xa-1. None of the bands are polymorphic within the
L. esculentum segregating population. These markers will be used
to study the sectoring mechanism if they can somehow be rendered
polymorphic within L. esculentum, which must be used when
studying the sectoring.
Return to Previous Page or Intl-PAG Homepage