RESEARCH REPORTS TGC REPORT 52, 2002
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potato leaf margin sometimes has a few rather wide and deep serrations (Fig 1e), but it
can be accurately identified with practice. The new phenotype was a monogenic
recessive to wild type based on the F1 and F2 results (Table 1). The new phenotype was
a monogenic dominant to c. The data suggest the new phenotype is allelic to c although
there were 2 plants that appeared to be wild type in the 745-Y1 x LA 2510 F2. These
may have been misclassified (although they were grown out and checked later) or due
to some type of error in the experiment. A closely linked gene to c can not be ruled out,
but it is felt that another allele at the c locus provides the best fit to the data. The symbol
c2 is thus proposed for the potato leaf allele derived from LA 1932.
It is surprising that this allele emerged from a cross of two non-potato leaf parents.
Possibly LA 1932 (sp+) is heterozygous for c2, although I do not remember seeing
indeterminate potato leaf
plants in any of our work. Apparently LA 1932 has a gene
linked on the opposite side of the sp locus (or very close to it) that is epistatic to c2
expression. The tomato yellow leaf curl virus (TYLCV) resistant variety ‘Tyking’ also has
a potato leaf type. Furthermore, we tested Henri Laterrot’s CHILTYLIC94-3 population
in 1995 and found a few plants showed ToMoV resistance. A few generations of
resistance selection followed and derived homozygous resistant lines all had potato
leaves. Since ‘Tyking’ is in the pedigree of the CHILTYLC94-3 population, this could
have been the source of the potato leaf. No allelism work has been done with c2 and
these other genotypes or with cint which has some similarity to c2 but a different length
/width ratio (see images in the TGRC website). It does seem probable that these
genotypes have a geminivirus resistance gene in the c region of chromosome 6. Lines
derived from LA 1932 with ToMoV and TYLCV resistance without c2 have recently been
developed,
indicating the linkage between c2 and the resistance gene has been broken.
Literature Cited
Griffiths, P.D. 1998. Inheritance and linkage of geminivirus resistance genes derived
from Lycopersicon chilense Dunal in tomato (Lycopersicon esculentum Mill.). PhD diss.,
Univ. of Florida, Gainesville.
Griffiths, P.D. and J.W. Scott. 2001. Inheritance and linkage of tomato mottle virus
resistance genes derived from Lycopersicon chilense accession LA 1932. J. Amer. Soc.
Hort. Sci. 126(4):462-467.
Scott, J.W. and D.J. Schuster. 1991. Screening of accessions for resistance to the
Florida tomato geminivirus. TGC Rpt. 41:48-50.
Tanksley, S. et al. 1992. High density molecular linkage maps of the tomato and potato
genomes. Genetics 132:1141-1160.
Weide, R. et al. 1993. Integration of the classical and molecular linkage maps of tomato
chromosome 6. Genetics 135:1175-1186.
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