Classic Genetics and Breeding - Genetics, Genomics and Breeding of Crop Plants - page 58

Figure 2-1 Use of marked genic male sterility in sunflower (genes Ms/ms : male fertile/
male sterile T/t : anthocyanin/non-anthocyanin.
with a heterozygous male fertile Ms/ms . It was thus necessary to eliminate
half of the plants in the rows of female parent, with a very dense sowing,
followed by thinning, which was costly and irregular.
The 1% recombination rate gave rise to male fertile plants not showing
anthocyanin, which produced pollen within the rows of females. Since bees
tend to remain on one genotype, the pollen from these male fertile female
plants was transferred by bees and pollinated up to 30% of the male sterile
plants around them. If they were removed by hand at flowering, this was
costly.
The discovery of a cytoplasmic male sterility (CMS) source by Leclercq
(1969), now known as PET1, from a cross between H. petiolaris and H. annuus,
simplified hybrid production since all female plants are male sterile
( Fig. 2-2 ) . Anthers of male sterile plants are very small and carry no visible
pollen at flowering. Most cultivated sunflower genotypes are CMS sterility
maintainers, but restorer genes were found in progenies from the same cross
and also in wild H. annuus and some other annual Helianthus species
(Kinman 1970; Leclercq 1971) . The first hybrids (FRANSOL and RELAX)
were registered in France in 1974 and cytoplasmic hybrids have been widely
grown in the world since 1978, and are now almost the sole type of variety.
This CMS source is used throughout the world for commercial hybrid
production. From other inter- or intra-specific crosses, about 20 other forms
of CMS have been obtained (Serieys 1999) with the idea that they would
constitute an insurance should any specific problem arise with the first
CMS. Studies on their possible agronomic interests indicated that specific
breeding programs would be necessary to obtain lines better than those
with the first CMS and these do not appear to have been undertaken.