Basic Information - Genetics, Genomics and Breeding of Crop Plants - page 37

induced tetraploids of H. annuus have also been obtained (Dhesi and Saini
1973). Jan et al. (1988) subjected growing points of young plants of inbred
lines P21 and HA 89 to a 5-h colchicine treatment at 1.5 g/kg, pH 5.4, with
20 g/kg dimethyl sulfoxide, resulting in a high frequency of chromosome
doubling and the production of autotetraploid P21 and HA 89. Tetraploidy
in P21 was not stable, with plants having 2 n = 4 x = 65 to 70 chromosomes.
Tetraploid plants of HA 89 had reduced vigor and did not produce achenes.
Reciprocal crosses of diploid and tetraploid P21 produced four triploid
plants. Backcrossing triploids to P21 produced 137 plants with 2 n = 34 to
47 + t . Thirty-one of these plants were trisomics having 2 n = 35.
Trisomic progenies of the 31 originally identified trisomic P21 plants
(Jan et al. 1988) only displayed limited variation in morphological
characteristics when grown in the greenhouse. Few trisomic groups appear
to have distinctive features such as unusual plant height, flowering dates,
leaf texture, and stem size. In order to quickly identify the first set of sunflower
trisomics, future research will need to be focused on the mitotic metaphase
and meiotic pachytene karyotyping, supplemented by the fluorescence in
situ hybridization (FISH) technique using linkage-group-specific restriction
fragment length polymorphism (RFLP) and BAC clones.
The same colchicine treatment on interspecific F 1 hybrids also resulted
in high frequencies of chromosome doubling and the production of
amphiploids (Jan and Fernández-Martínez 2002). The tetraploid
amphiploids produced included crosses of P21 x H. bolanderi (Jan and
Chandler 1989), H. gracilentus x P21, H. grosseserratus x P21, H. cusickii x P21,
H. mollis x P21, H. maximiliani x P21, and H. nuttallii x P21. These
amphiploids have restored fertility, and provide additional genetic diversity
for the improvement of cultivated sunflower. They can be backcrossed with
cultivated lines without the use of embryo culture to produce progenies. An
amphiploid of H. hirsutus x P21 represents the first hexaploid amphiploid
in sunflower. Like the autotetraploid P21, the amphiploids were not
completely stable. After sib-pollination of 2 n = 68 amphiploids, progenies
could have 2 n chromosome numbers from 64 to 71. The sib-pollination of 2 n
= 102 H. hirsutus x P21 amphiploid produced progenies with 2 n chromosome
numbers from 94 to 103. Additional hexaploid amphiploids of H. hirsutus x
P21 and H. strumosus x P21 were also produced.
It is expected that interspecific amphiploids will enable the establishment
of a number of chromosome addition lines for genetic studies of specific
chromosomes of both cultivated and wild Helianthus species. With the
available amphiploids and some specific interspecific crosses, the potential
exists to establish addition lines with HA 89 chromosomes in H. californicus
cytoplasm and the chromosomes of H. hirsutus , H. angustifolius , H. cusickii ,
H . gracilentus , H. grosseserratus , H . nuttallii , H. strumosus , and H. giganteus in
HA 89 cytoplasm (Jan and Seiler 2007).