Classic Genetics and Breeding - Genetics, Genomics and Breeding of Crop Plants - page 78

2.7 The introduction of Genomics in Breeding Since 1995
In addition to changes in ideas about breeding programs, molecular studies
and genomics have already been used to reduce the cost of some operations
or to speed up conventional breeding programs. In the course of registration
of a hybrid variety on official catalogs in Europe, checks are made to ensure
that the hybrid tested comes from the parental inbred lines declared. In the
past, the lines were crossed to reproduce the hybrid and its phenotype was
compared with that of the seed provided by the breeder. For the last 10 years,
this check has been made by genotypic analyses to show that the genotype
of the hybrid is compatible with the genotypes of the parental lines. This
was done first with isoenzyme systems, but, since 2007, microsatellite
markers have been used. Breeders also make such analyses to check the
homozygosity of their new lines before protection or commercialization.
The first real use of molecular markers in breeding has been in backcross
programs to introduce downy mildew or broomrape resistance or the high
oleic character, taking advantage of markers that are very closely linked or
part of the genes concerned that have been identified in genetic and genomic
studies of these characters (Lacombe and Berville 2001; Radwan et al. 2002).
Molecular analyses on small pieces of young leaves of individual plants
make it possible to determine those of interest (which may be only 1 in 10 in
progeny from crosses between two male fertile plants), before flowering and
thus to reduce the number of plants to be bagged and harvested and the
need for phenotypic analyses before starting the following generation.
Another use which is now starting is to follow segments of chromosomes
from wild Helianthus in introgression programs, to make sure that selection
for all the favorable characters of cultivated sunflower does not eliminate
all the wild genome. Even if it may be some time before sunflower breeding
for yield using QTL markers becomes a reality, it should be possible in the
next few years to use molecular markers of simpler characters contributing
to yield, such as leaf area, self-fertility or seed size, to select in early
generations (F 2 ) and only make hybrids to be tested for yield in the field,
with plants that have the favorable alleles for quite strong QTL.
References
Baldini M, Cecconi F, Cecchi A, Martorana F, Vanozzi GP, Benvenuti A (1996) Drought
resistance in sunflower. Factors affecting yield and their variability under stress.
Proc 13th Int Sunflower Conf, Pisa, Italy, vol 1, pp 513-521.
Bert PF, Tourvieille de Labrouhe D, Philippon J, Mouzeyar S, Jouan I, Nicolas P, Vear F
(2001) Identification of a second linkage group carrying genes controlling resistance
to downy mildew ( Plasmopara halstedii ) in sunflower ( Helianthus annuus L.). Theor
Appl Genet 103: 992-997.
Bert PF, Dechamp-Guillaume G, Serre F, Jouan I, Tourvieille de Labrouhe D, Nicolas P,
Vear F (2004) Comparative genetic analysis of quantitative traits in sunflower