8th INTERNATIONAL WHEAT CONFERENCE

PRoBLemS ShouLd Be PAId ATTeNTIoN IN CRoP
moLeCuLAR BReedINg
Wang Haibo
Plant Genetic Engineering Center, Institute of Genetics and Physiology, Hebei Academy of
Agriculture and Forestry of, Shijiazhuang 050051
E-mail Address of presenting author:
1. The relativity of pure lines interfering the accuracy of molecular markers
Theoretically, pure line can be obtained by self-pollination and selection, but actually it is
impossible in practice. Biological traits can be classified as distinguishable traits and nondistinguishable
traits. The distinguishable traits can be further divided into visible traits
and non-visible traits, and most of the traits are non-visible. Even for the visible traits,
only a few has been well-mastered. If the traits are unclear, it can not conduct molecular
genetic investigation and correspond to the DNA sequences, the power of molecular
markers will be stopped at concept level. Generally, crop genomes are very large, the
genes not only are installed in different chromosomes, but also are exchanged between
the homologues. It results in a huge number of gamete types and homozygous types.
The probability of heterozygosity among alleles is 50%, while the events of combination
of non-allelic genes would be nearly infinite. Thus, a variety can not become a real pure
line without double haploid procedure. Through traditional continuous backcrossing, the
near-isogenic lines can not be produced and molecular genetic research can not find the
real results.
2. Molecular breeding facing a serious challenge of background constraints
The results are usually undesirable in molecular breeding, whether it come from genetic
transformation or marker-assisted selection or molecular design. The objective gene
could not display the expected role because it does not match the genetic background
well. In the past, the function of genetic background is usually consciously avoided since
it is very complicated, but it has reached the point that it can not be further continued.
Thus, to carry out the research of genetic background and gene sociology is urgent. Based
on continuous backcrossing, to track and compare the molecular map between different
generations and their corresponding pollens using high-resolution molecular makers,
some patterns of genetic background and the interaction of objective gene with genetic
background can be found.
3. The gene of Mendelian factor much complicated than DNA sequence
According to Mendel’s idea, traits are always correspond to genes, the Mendelian factor
equals gene. At the molecular level, gene is a specific DNA sequence. However, DNA
sequence variation does not surely show a trait. Mutant-genetics have shown that thousands
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