Rick, C. M. Petroselinum (Pts), a new marker for chromosome 6.
L. cheesmanii f. minor is characterized by highly compound leaves (see front cover). In F2 f. minor X L.
esculentum and various BC derivatives of this cross, the progenies clearly segregate for this character vs. normal.
For such segregations, which we have observed repeatedly, the following data are typical. Crosses were made
between cv. VF 36 and four accessions of f. minor (LA 530, 532, 930, and 1136); 2 backcrosses to VF 36; and selfs
of compound leaved segregants. Since segregation in each family was similar, the data were pooled to yield the
totals of 53 normal, 118 intermediate, and 56 compound. The fit to 1:2:1 is good, as manifest in the x2 (0.426). The
compounding of leaf segments to 3rd and even 4th order is clearly expressed in the homozygotes, and the
intermediate phenotypes obviously deviate from normal. The evidence therefore indicates the activity of an
incompletely dominant gene, which is designated Petroselinum (Pts) for the resemblance to plain parsley foliage.
Since sp segregated in all families, it was also scored with the following dual segregation:
This segregation deviates markedly from random and indicates linkage between Pts and sp. A maximum likelihood
test by Steve Tanksley provides an estimate of 12.5 cM for the sp-Pts interval. Without a 3-point test or other data, I
cannot be certain of the locus of Pts except that it certainly lies on 6L.
Robinson, R. W. Pleiotropic effects of the j-2 gene.
The jointless-2 gene is being used increasingly by tomato breeders. It provides resistance to premature
separation and loss of fruit during mechanical harvest and increases the proportion of stem-free fruit. Jointless-2
cultivars have been developed which do not have the delayed and poor concentration of maturity found by Emery
and Munger (J. Am. Soc. Hort. Sci. 95:407-41.0, 1970) to be associated with j-2
The j-2 gene was backcrossed to New Yorker to develop isogenic lines. Selfing for 3 generations after the
sixth backcross resulted in a j-2/j-2 line identical to the recurrent parent and in a homozygous jointless-2, essentially
isogenic, line.
Although j-1 reduces the number of flowers per inflorescence, j-2 has the opposite effect. The jointless line
had an average of 45.8 flowers per inflorescence, compared to 6.1 for the normal counterpart. The superfluous
flower production did not increase fruit production, however, since fruit set was reduced by j-2. Only 1.4 fruit per
cluster developed on j-2 plants, in contrast to 6.1 for the + line, an average fruit set on the first two clusters of 3.1%
for the jointless and 52.5% for the jointed line. The anthers of the j-2 line were often not tightly united around the
style, possibly reducing fruit set by restricting pollination.
Leaves occasionally developed in inflorescences of the j-2 but not the + line, similar to the effect that Rick
and Sawant (Proc. Am. Soc. Hort. Sci. 66:354-360, 1955) noted was produced in sp plants by j-1 and other genes
affecting development of the abscission layer. Earliness was delayed and yield reduced by j-2. The fruit of the
jointless line differed from normal by being larger, flatter, rougher, and catfaced, and having more tightly attached
stems and larger sepals, stem scars, and cores.
Adverse effects of the j-2 gene can be modified by breeding. Breeders have developed j-2 cultivars without
excessive flowers per inflorescence, poor fruit set, and malformed fruit. But their success does not appear to be due
to crossing-over, separating j-2 from closely linked undesirable genes. When jointless-2 cultivars with normal
inflorescence and good fruit set and type were used as parents, there was an association in segregating
generations between j-2 and
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