Complete volume with articles 1 to 32 - Cucurbit Breeding - North ...

to determine seed size for the long, medium,
and short classes (ll SS for long, LL SS for
medium, and LL ss or ll ss for short). The
tomato seed size was studied in a cross
between a 'Sugar Baby' mutant with tomato
seed size and 'GN-1', with short seeds. The
tomato seed size trait was inherited as a single
recessive gene (ts) (58). The interaction of ts
with l and s has not been described so far. In
addition, a gene (Ti), dominant over medium
seeds, has been described for the so-called
"tiny" seed-size in 'Sweet Princess' (50). Tiny
seeds have size similar to small seeds (Fig. 2).
The main colors of watermelon seeds are
white, tan, brown, black, red, green, and
dotted (24). In addition, seeds may have
lighter or darker margins (ring), or may be
covered by an additional layer of fleshy
pericarp in Egusi cultivars, as controlled by
the eg gene (Fig. 1) (12, 13).
The genes r, t, and w determine seed color.
Black is given by triple dominant; mottled is
homozygous recessive only for w; tan is
homozygous recessive only for t; white with
tan tip is homozygous recessive only for t and
w; red is homozygous recessive only for r and
t. Finally, triple recessive results in white
seeds with pink tip (34). The dotted (renamed
from mottled) seed type is determined by the
d gene, acting as a modifier of black: RR TT
WW DD gives solid black and RR TT WW dd
gives dotted black seed-coat (20, 32, 34).
Seeds of certain cultivars show vertical cracks
(parallel to the longest axis of the seed) of the
seed-coat, usually less than one mm wide and
about 50-75% of the seed length. The
development of these cracks has been
determined to be under the genetic control of
cr (1). It is not known if this phenotype has
any advantage in germination and whether
growers would perceive seeds with cracks as
defective, compared to normal seeds.
Other genes of minor interest to breeders have
been studied and described, as reported in the
current watermelon gene list (11). These
include genes for green flower color (gf),
golden leaf color (go), along with several
genes coding for specific proteins. In
addition, watermelon breeders have selected
for many different characteristics, such as
flesh color, rind pattern, plant architecture,
and leaf shape, for which the inheritance is
unknown so far. Efforts are under way to
collect mutants for storage and distribution by
the Cucurbit Genetics Cooperative
watermelon gene curators (T.C. Wehner and
S.R. King).
Literature Cited
1. Abd el Hafez, A. A., A. K. Gaafer, and A.
M. M. Allam. 1981. Inheritance of flesh
colour, seed coat cracks and total soluble
solids in watermelon and their genetic
relations. I. Quantitative traits. Acta
Agronomica Academiae Scientiarum
Hungaricae 30:82-86.
2. Abd el Hafez, A. A., A. K. Gaafer, and A.
M. M. Allam. 1985. Inheritance of flesh
colour, seed coat cracks and total soluble
solids in watermelon and their genetic
relations. II. Quantitative characters and
the association between various
characters. Acta Agronomica Academiae
Scientiarum Hungaricae 34:84-89.
3. Boyhan, G., J. D. Norton, and B. R.
Abrahams. 1994. Screening for resistance
to anthracnose (race 2), gummy stem
blight, and root knot nematode in
watermelon germplasm. Cucurbit
Genetics Cooperative Report 17:106-110.
4. Brar, J. S., and K. S. Nandpuri. 1974.
Inheritance of fruit weight in water-melon
[Citrullus lanatus (Thunb.) Mansf.].
Journal of Research, Punjab Agricultural
Service 11:140-144.
5. Brar, J. S., and K. S. Nandpuri. 1977. A
note on the inheritance of total soluble
solids in watermelon (Citrullus lanatus
(Thunb) Mansf.). Haryana Journal of
Horticultural Sciences 6:193-195.
6. Brar, J. S., and A. S. Sidhu. 1977.
Heterosis and combining ability of
earliness and quality characters in
56 Cucurbit Genetics Cooperative Report 28-29: 52-61 (2005-2006)