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[Only registered and activated users can see links. Click Here To Register...] [Ramón Pérez] wrote...

Don't know [But why should all grape seedless variants necessarily
have to be similar to one another? Weren't there multiple independent
origins of seedless varieties, possibly involving different genes and
different mutations?].

Anyway, it's not my area, but results of a quick Biological Abstracts
database search include a few more recent citations-with-abstracts
that may be of interest to you:

Title: Genetic mapping of grapevine (Vitis vinifera L.) applied to the
detection of QTLs for seedlessness and berry weight.
Author, Editor, Inventor: Doligez-A {a}; Bouquet-A; Danglot-Y;
Lahogue-F; Riaz-S; Meredith-C-P; Edwards-K-J; This-P
Source: Theoretical-and-Applied-Genetics. [print] October, 2002; 105
(5): 780-795.
Abstract: Parental and consensus genetic maps of Vitis vinifera L.
(2n=38) were constructed using a F1 progeny of 139 individuals from a
cross between two partially seedless genotypes. The consensus map
contained 301 markers (250 amplification fragment length polymorphisms
(AFLPs), 44 simple sequence repeats (SSRs), three isozymes, two
random amplified polymorphic DNAs (RAPDs), one sequence-characterized
amplified region (SCAR), and one phenotypic marker, berry color)
mapped onto 20 linkage groups, and covered 1,002 cM. The maternal map
consisted of 157 markers covering 767 cM (22 groups). The paternal
map consisted of 144 markers covering 816 cM (23 groups). Differences
in recombination rates between these maps and another unpublished map
are discussed. The major gene for berry color was mapped on both the
paternal and consensus maps. Quantitative trait loci (QTLs) for
several quantitative subtraits of seedlessness in 3 successive years
were searched for, based on parental maps: berry weight, seed number,
seed total fresh and dry weights, seed percent dry matter, and seed
mean fresh and dry weights. QTLs with large effects (R2 up to 51%)
were detected for all traits and years at the same location on one
linkage group, with some evidence for the existence of a second linked
major QTL for some of them. For these major QTLs, differences in
relative parental effects were observed between traits. Three QTLs
with small effects (R2 from 6% to 11%) were also found on three other
linkage groups, for berry weight and seed number in a single year,
and for seed dry matter in 2 different years.

Title: Breeding and genetic study on hybrid combinations between
seeded and seedless grapevine (Vitis vinifera L.) cultivars.
Author, Editor, Inventor: Roytchev-V {a}
Source: Genetics-and-Breeding. [print] 2000; 30 (1-2): 35-47.
Abstract: Through breeding and genetic investigations in F1 progeny
of hybrid combinations between seeded and seedless grapevine
cultivars, it was established that berry size, shape and weight are
polymeric traits, inherited through incomplete dominance of cultivars
with smaller and round berries. The phenotypic manifestation of seed
weight and number in seeded forms confirmed that berry seedlessness
is determined by dominant genes, too. To develop new high-yielding
elongated seedless grapevine cultivars it is necessary to cross
large-fruited parent cultivars with oblong berries, and selection
should be done on a large number of plants.

Title: A stenospermocarpic, seedless Vitis vinifera X Vitis
rotundifolia hybrid developed by embryo rescue.
Author, Editor, Inventor: Ramming-David-W {a}; Emershad-Richard-L;
Tarailo-Ronald
Source: Hortscience-. [print] July, 2000; 35 (4): 732-734.
Abstract: Hybridizations between seedless Vitis vinifera L. genotypes
and V. rotundifolia (Michx.) were made specifically to introgress the
seedless trait into the disease-resistant background of V.
rotundifolia. The seedless, gynoecious P79-101 was hybridized with
three V. rotundifolia parents, producing a total of 102 ovules. From
these ovules, 44 embryos developed, producing 20 plants. Isozyme
analyses and morphological traits confirmed that 19 of the plants were
hybrids. Sixteen were planted in an experimental vineyard at California
State Univ. Fresno. One seedling, C41-5, produced seedless fruit that
appeared to be stenospermocarpic based on fruit and aborted seed size.
Fruit weight was slightly less than that of 'Thompson Seedless'
(stenospermocarpic) and at least twice that of parthenocarpic fruit of
'Black Corinth' and C41-7, a seeded hybrid with many parthenocarpic
fruit. Aborted seeds of C41-5 were larger than, but not significantly
different from,those of 'Thompson Seedless', while parthenocarpic fruit
from 'Black Corinth' and C41-7 had aborted seeds that were smaller than
those of C41-5. Seed weight of C41-7 averaged almost 10 times that of
aborted C41-5 seeds. This is the first report of a stenospermocarpic,
seedless hybrid of V. vinifera X V. rotundifolia.

Title: Identification of a codominant scar marker linker to the
seedlessness character in grapevine.
Author, Editor, Inventor: Lahogue-F {a}; This-P; Bouquet-A
Source: Theoretical-and-Applied-Genetics. Oct., 1998; 97 (5-6) 950-959.
Abstract: The variety Vitis vinifera cv Sultanine presents a type of
seedlessness in which fertilization occurs but seeds subsequently fail
to develop. It has been suggested that this trait might be controlled
by three complementary recessive genes regulated by a dominant gene
named I. Bulk segregant analysis was used to search for random
amplified polymorphic DNA (RAPD) markers linked to the I gene in
progeny obtained by crossing two partially seedless genotypes. One
hundred and forty decamer primers were screened using bulks obtained
by pooling the DNA of extreme individuals from the phenotypic
distribution. We identified two RAPD markers which appeared tightly
linked to I (at 0.7 and 3.5 cM respectively). The closest marker was
used to develop a codominant SCAR (sequence characterized amplified
region), named SCC8. This latter marker appeared of great value either
to exclude from the progeny potentially seeded individuals or to select
for seedless individuals. Indeed, all the seeded individuals of the
progeny were found to be homozygous scc8-/scc8-,and all the individuals
homozygous SCC8+/SCC8+ were seedless. Moreover, this marker was
successfully applied to other natural seedless varieties where
codominance persisted. SCC8 was also used to dissect more precisely
the genetics of seedlessness. ANOVA analysis indicated that this SCAR
marker accounted for at least 64.9% of the phenotypic variation of
the seed's fresh weight and for at least 78.7% of the phenotypic
variation of the seed's dry matter. These results confirmed the
presence of a major gene, and also the existence of other
complementary recessive genes, controlling the expression of
seedlessness.

Title: Influence of grape genotype, ripening season, seed trace size,
and culture date on in ovule embryo development and plant formation.
Author, Editor, Inventor: Pommer-Celso-V {a}; Ramming-David-W;
Emershad-Richard-L
Source: Bragantia-. 1995; 54 (2) 237-249.
Abstract: Eighteen seedless grape genotypes differing in ripening
season (early, mid and late) and in seed trace size (small, medium
and large) were harvested at 6, 10, 14, 18 and 22 weeks past bloom
(wpb). Using embryo rescue techniques it was studied if embryo do
abort as the fruit matures and what percent embryos remain viable at
later stages. The size of seed trace was also investigated to determine
its influence on embryo viability during maturation. It was found that
genotype have great influence on embryo culture traits. Late maturing
genotypes showed fewer rescued embryos, germinated embryos and
transplantable plants than early and mid season ones. The best
culture time for grape embryo rescue is 6 and 10 wpb. At these dates,
the largest number of embryos, germinated embryos and transplantable
plants were obtained. Genotypes with the largest ratio for seed trace
weight/seed trace length (i.e., largest density) showed the greatest
tendency to have the largest number of ovules with embryos, more
germinated embryos and more transplantable plants. The study also
showed that it is possible to recover plants from mature fruit
harvested late, although at a much reduced rate.

Title: Identifying molecular genetic markers associated with
seedlessness in grape.
Author, Editor, Inventor: Striem-M-J; Ben-Hayyim-G; Spiegel-Roy-P {a}
Source: Journal-of-the-American-Society-for-Horticultural-Science.
1996; 121 (5) 758-763.
Abstract: Excluding seeded offspring at an early stage could be of
great value to the breeder concerned with the development of seedless
grapes (Vitis vinifera L.). We used the random amplified polymorphic
DNA (RAPD) technique to identify molecular genetic markers, analyzing
82 individuals of a progeny resulting from a cross between 'Early
Muscat' (seeded) and 'Flame Seedless'. Seven variables representing
the traits of seedlessness were analyzed: mean fresh weight of one
seed, total fresh weight of seeds per berry, perception of seed content,
seed size categories evaluated visually, degree of hardness of the seed
coat, degree of development of the endosperm, and degree of development
of the embryo. Among 160 10mer primers, 110 gave distinct band patterns.
Twelve markers yielded significant correlations with several subtraits
of seedlessness, mainly with the mean fresh weight of one seed and the
total fresh weight of seeds per berry. Multiple linear regression
analysis resulted in high coefficients, such as R = 0.779 for fresh
weight of seeds per berry, when the seven markers were included as
independent variables in the model. Most of the seeded individuals,
about 44% of the progeny, could be excluded using a two-step process
of marker assisted selection.

Title: Inheritance of stenospermocarpic seedlessness in Vitis vinifera L.
Author, Editor, Inventor: Ledbetter-C-A; Burgos-L
Source: Journal-of-Heredity. 1994; 85 (2) 157-160.
Abstract: The inheritance of stenospermic seedlessness in Vitis vinifera
L. was studied in F-1 populations obtained from seeded by seedless
crosses. Two distinct types of stenospermic male parents were used.
Male parents were obtained either from the progeny of seeded by seedless
crosses or from in ovulo embryo cultures of seedless by seedless
hybridizations. Based on the segregation ratios of progeny populations,
an inheritance model for the stenospermic trait is proposed, consisting
of three dominant complementary factors. Three independently inherited
genes are necessary to produce a seedless phenotype. A homozygous
recessive condition at any of the three loci would produce a seeded
phenotype. Emphasis is placed on the high percentage of seedlessness
obtained in crosses where the males used were derived from seedless by
seedless progenies.

Title: INHERITANCE STUDIES OF SEEDLESSNESS IN GRAPES.
Author, Editor, Inventor: LOOMIS-N-H {a}; WEINBERGER-J-H
Source: Journal-of-the-American-Society-for-Horticultural-Science.
1979; 104 (2): 181-184.
Abstract: More than 10,000 seedlings were studied to elaborate the mode
of inheritance of seedlessness in grapes (Vitis spp.). Self-pollinations
of seeded selections having seedlessness in their parentage gave 0-10.7%
seedless progeny. Crosses between seeded selections with seedlessness in 1
or both parents gave similar proportions. Crosses of seeded .times.
seedless selections gave 0-55% seedless. Results were extremely variable,
without apparent correlation to normal genetic ratios. Seedlessness
appeared to be largely controlled by recessive factors.

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