Chromosome regions with multiple effects.<p>

Williams, W.  <p>

The chromosome regions denoted by macrocalyx and jointless pedicel are known
to produce effects on the phenotype which are additional to the characters
implied in their naming. The gene lateral suppressor (ls) causes a syndrome of
characters comprising suppression of lateral branches, suppression of the
corolla, incohesion of the anthers, as well as a severe reduction in the
number of flowers per truss.  Observations on F2 progenies segregating for ls
mc and j yield further information on the composition of these regions.<p>
<pre>

                   Cross    Cross    "double"
Region    Normal   Over 1   Over 2   recessive

 mc        603       0        0         214
  j        739       0        0         253
 ls     16,334       0        0        5232
</pre>
     
The figures of ls segregations refer to recombination between effects on
lateral branches and on the corolla and if the expressions are governed by
closely linked genes the frequency of recombination must be extremely low.
Homozygous ls ls phenotypes out of F1 hybrids involving L.  pimpinellifolium
showed small quantitative modification of corolla development, but nothing
approaching a cross-over was recovered.  F2 families derived from crosses
between diverse varieties of L. esculentum failed to produce any modification
of the corolla among the lateral suppressor phenotypes.  These results are not
inconsistent with the differential modification of pleiotropic effects by
changes in the gene background and they provide no valid reason for the
creation of hypothetical linkages to explain such multiple effects which may
well be based on a common metabolic process. <p>
 
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