Basic Information - Genetics, Genomics and Breeding of Crop Plants - page 44

progenies exhibited substantial genetic distance from their parental
sunflower inbred lines, and hybrids having reduced Sclerotinia infection
were identified.
Hu and Vick (2003) developed a new marker technique, “target region
amplification polymorphism” (TRAP), which uses bioinformatics tools and
expressed sequence tag (EST) database information to generate polymorphic
markers around targeted gene sequences. This technique has been successful
in constructing a phylogenetic tree of 16 perennial Helianthus species (Hu et
al. 2003) and assessing the genetic diversity and relationship among 177
USDA-ARS released public sunflower inbred lines (Yue et al. 2009).
1.7 Conclusions
Sunflower production continues to face challenges from both abiotic and
biotic factors as well as from today's ever-changing market needs as production
is shifting from areas of high productivity to marginal areas with lower yield
potential. The challenge for the sunflower community is to breed sunflower
adaptable to these marginal environments and at the same time increase seed
yield. The crop has been faring quite well; however, the marked reduction in
genetic diversity during domestication of the cultivated sunflower crop has
placed the crop in a vulnerable position should any major shifts of disease
races or pests occur. The uniform use of a single CMS PET1 (French) cytoplasm
and a few fertility restoration genes for worldwide hybrid sunflower
production makes the crop extremely vulnerable. Wild species of sunflower
have been a source of many genes for pest resistance, especially for diseases.
They also serve as the female parent for all hybrid sunflowers. Since wild
sunflower and the sunflower crop are native to North America, associated
pests have co-evolved in natural communities, thus providing the opportunity
to search for pest resistance genes in the diverse wild species.
Significant advances have been made in understanding the origin,
domestication, and organization of the genetic diversity, characterization,
and screening methods for abiotic and biotic stresses. Useful germplasms
have been identified for many agronomic traits and MAS is beginning to be
used for selection of favorable alleles and QTLs. Molecular biology has
added to the scope of plant breeding in sunflower, providing an option to
manipulate plant expressions. The process has barely begun, but there is
great opportunity to address all aspects of crop production, utilization, and
food value. Similarly, more integrated linkage maps are becoming available.
Researchers will have to strive to combine the best conventional and modern
molecular approaches to improve sunflower germplasm to keep sunflower
an economically viable global crop. This will require a multidisciplinary
team approach and a commitment to a long-term integrated genetic
improvement program.