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Rice Genomics and Genetics 2012, Vol.3, No.7, 39
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improved in the seedling stage, the injury of the cell
membrane of the positive plants reduced, the vitality
of the leaf enhanced and the salt tolerance increased.
Zhi et al (2005) transferred the leguminous plant gene
P5CS
(2-hydrogen pyrrole 5-carboxylic acid synthase)
into rice via the gene gun bombardment, and found
that the content of the praline and the salt tolerance of
transgenic rice also increased. Katsuhara et al (2003)
transferred the gene encoded a water channel protein
on the plasma membrane of the barley into rice and
made it over-express, then they found that the ratio of
the stem to the root in transgenic rice increased, while
the sensitivity to salt stress of transgenic rice
decreased. Li and Guo (2006) transferred the salt
tolerance gene
OPBP1
into rice via the gene gun
bombardment, and the result showed that the
transgenic plants grew fast, the chlorophyll content
and biomass were significant higher than that of the
control. Guo (1997) and Su (1999) transferred the
single gene
mtlD
(1-phosphate mannitol dehyd
rogenase gene) and
gutD
(6-phosphate sorbitol
dehydrogenase gene) or the bivalent gene
CMO/
BADH
(choline monooxygenase gene/betaine aldehyde
dehydrogenase base) into rice, and both all obtained
the transgenic plants which the salt tolerance had
enhanced.
Guo et al (2006) transferred the 5 genes related to salt
tolerance
CMO, BADH, mtlD
(1-phosphate mannitol
dehydrogenase gene),
gutD
and
SAMDC
(S-
adenosylmethionine decarboxylase gene) into
conventional japonica Xiushui 11, Zhonghua 11,
indica Teqing and the restorer lines Minghui63 via
Agrobacterium
-mediated transformation and the gene
gun bombardment, and combined with conventional
hybridization breeding to polymerize pentavalent gene,
then Xiushui 11 with 9 different genotypes were bred,
among which the best line was selected, finally they
got 9 combinations lines (8 single, bivalent, trivalent
genes, and one pentavalent gene, the phenotypes all of
these lines were similar to Xiushui 11, and the number
were TX
4
CMO
-4-13-6, TX
4
MtlD
-5-9-12, TX
4
BADH
-12-3-7,
TX
4
GutD
-14-9-7, TX
4
SAMDC
-11-3-8, TX
4
CMO / BADH
-10-3-9,
TX
4
MtlD / gutD
-7-9-14, TX
4
mtlD / gutD +SAMDC
-16-4-9 and
FX
5
pentavalent
-3-7), and the comprehensive assessment
and the study of rational use were done in the southern
part of Zhejiang Province.
4.3 The molecular breeding of two types of salt
tolerance genes polymerization
Along with the development of genomics, gene
pyramiding will be the most effective way to
improve and cultivate the high-yielding rice
varieties (Guo et al., 2008; Liu et al., 2003;
Basharat et al., 2006). It will contribute to further
improve the salt tolerance and breed the high salt
tolerance variety to polymerize genes in different
salt tolerance pathway. At present, two types of salt
tolerance genes were used for breeding. One type
was the genes
CMO
,
BADH
,
mtlD
,
gutD
and
SAMDC,
which was resistant to the water stress and
regulate small-molecules like lycine; the other was
anti ion toxicity gene
SKC1
(Ren et al., 2005).
In 2005, we started to polymerize the above two types
genes through combining the transgenic and the
conventional breeding, which was based on the
breeding of
CMO
/
BADH
transgenic rice
and the
marker-assisted selection of
SKC1
resistant to salt
tolerance, we wanted to obtain the salt tolerance rice
with the genes in different salt tolerance pathway, to
explore the genetic mechanism and interaction
regulations of the two types genes and to improve the
resistance to environmental stress and the commercial
value of the genes (Figure 1). We had obtained a series
of salt tolerance strains with the genes in different salt
tolerance pathway by polymerizing two types of
resistance genes molecular markers, which was
funded by National 863, for example, Yueguang-
SKC1
/BADH
-12 and Xiushui 11-
SKC1/BADH
-23 could
return to normal growth after treated in 1.0% NaCl.
And the new stain Yuexiu T22-77 derived from
transferring
BADH/SKC1
into rice has already applied
to the Ministry of Agriculture for intermediate
experiment. The rice combinations polymerizing two
types of resistance genes will process the wide
resistance to environmental stress, the commercial
value and application prospect.
5 Prospects
Plant salt-tolerance mechanisms have already been
researched several decades and gotten many valuable
achievements. This brings dawn to molecular