Basic Information - Genetics, Genomics and Breeding of Crop Plants - page 36

the time of its discovery and its reaction to restoration testers, is widely
accepted among sunflower researchers.
1.5.5.6 Salt Tolerance
Several species of Helianthus are native to salt-impacted habitats. Interspecific
germplasm with high salt tolerance withstanding salt concentrations up to
EC 24.7 d/Sm have been identified from annual H. paradoxus . It appears
that one major gene controls salt tolerance, although a modifier gene may
also be present, possibly recessive in control (Miller 1995). Two salt-tolerant
parental oilseed maintainer lines, HA 429 and HA 430, have been released
(Miller and Seiler 2003).
1.5.5.7 Herbicide Tolerance
A wild population of annual H . annuus from a soybean field in Kansas, USA,
that had been repeatedly treated with imazethapyr chemical for seven
consecutive years developed resistance to the imidazolinone and
sulfonylurea herbicides (Al-Khatib et al. 1998). Resistance to imazethapyr
and imazamox herbicides has great potential for producers in all regions of
the world for controlling several broadleaf weeds. Several populations of
wild sunflower ( H . annuus and H . petiolaris ) from the USA and Canada have
been screened for resistance to these two herbicides. Eight percent of 50
wild sunflower populations had some resistance to imazamox and 57%
had some resistance to tribenuron in the central USA (Olson et al. 2004). In
Canada, 52% of 23 wild H . annuus populations had some resistance to
tribenuron (Miller and Seiler 2005). Genetic stocks IMISUN-1 (oil maintainer),
IMISUN-2 (oil restorer), and IMISUN-3 (confection maintainer) have been
developed and released (Al-Khatib and Miller 2000). Miller and Al-Khatib
(2002) also released one oilseed maintainer and two fertility restorer breeding
lines with imidazolinone herbicide resistance. Genetic stocks SURES-1 and
SURES-2 with resistance to the sulfonylurea herbicide tribenuron have been
developed and released by Miller and Al-Khatib (2004). In addition, the two
herbicides may control broomrape in areas of the world where this parasitic
weed attacks sunflower (Alonso et al. 1998).
1.5.6 Cytogenetic Stocks
Induction of polyploidy in sunflower has been accomplished using
colchicine. Heiser and Smith (1964) grew seedlings for 8 h on filter paper
saturated with a 2.0 g/kg solution of colchicine and obtained some
chromosome doubling. Using this technique, they obtained tetraploids from
the perennial hybrid cross H. giganteus x H. microcephalus . Colchicine-