Page 8 - 2012RGGV3NO7

Rice Genomics and Genetics 2012, Vol.3, No.7, 39-49
http://rgg.sophiapublisher.com
43
Continuing table 1
Name of variety (line) Source Leading features
Shengshuilian China Salt-tolerance, waterlogging-tolerant(deep water), strong resistance to disease and
insect, late indica
Xianzhan China Salt-tolerance, waterlogging-tolerant(deep water), strong resistance to disease and
insect, late indica
Damangdao China Salt-tolerance, high yield
Laohuangdao China Salt-tolerance, high quality, easy lodging, can be used as salt-tolerant parents
Gaoliangdao China Salt-tolerance, high yield
Liaoyan 2 China High salt-tolerant, high yield, wide adaptability
Changbai 7 China Salt-tolerance, high quality, good agronomic traits
3 The genetic and molecular mechanism of
the salt tolerance of rice
The salt tolerance of rice is the genetics of quantitative
characters, which is controlled by multiple genes (Lin
et al., 2004). The geneticists had mapped more than 70
QTLs which were related to the salt tolerance with the
RIL and DH populations (Table 2), and two important
salt tolerance genes of rice (SKC1 and DST) have
already been cloned.
3.1 Mapping of the salt tolerance QTL of rice
The indicators of the salt tolerance mainly included
the survival days in salt stress, salt damage level and
Na+/K+ traits. So far, about 70 salt tolerance QTLs had
been located (Zang et al., 2008). Lin et al (1998)
detected one QTL (RG13) which was significant
correlation with the salt tolerance on the chromosome 5
using the RIL population (Aishante 2/CB), and the locus
could explain 11.6% of the phenotypic variances. Gu
et al (2000) mapped 4 salt tolerance QTLs which
affected the salt damage level and Na+ content in
seedling with the BC1 population which was derived
from the salt tolerance variety (Pokkali) and the salt
sensitive variety (Peta), and found that 12 QTLs
which affected the salt tolerance in mature stage
distributed in 1 or 2 linkage interval of chromosome 7.
Gong et al (Chinese Science Bulletin, 43(17):
1847-1850) mapped 7 QTLs of the survival days of
seedling using the DH population which was derived
from Zaiyeqing 8 and Jingxi 17 in 1998; he also
investigated the differential expression of five
important agricultural traits in the salt stress and the
non-salt stress condition in 2000, and detected 17
QTLs (Gong et al., Science in China Series C, 30(6):
561-569). Koyama et al (2001) found 10 QTLs related
to the Na +/K+ absorb of the stem and the leaf by
employing the RILs population of IR4630/IR15324.
Yao (2002) constructed the F2 population with
Jiucaiqing and IR36 to detect the salt tolerance QTL in
seedling stage by interval mapping, through which he
reported 3 QTLs affecting salt damage level were
located on chromosome 1, 5 and 9, respectively, 2
QTLs affecting Na +/K+ absorb of the root were
located on chromosome 2 and 6, the QTLs affecting
fresh weight of stem and leaf and the QTLs affecting
dry weight of stem and leaf was mapped in the same
interval, and located on chromosome 8 and 9,
respectively, 2QTLs affecting the root length of the
seedling were located on chromosome 4 and 5. Lin et
al (2004) detected 11QTLs correlated with the
survival days of seedling, Na + /K+ absorb of the stem,
the leaf and the root, which will pave the way for the
further fine-mapping and cloning research.
3.2 Cloning of the salt tolerance gene of rice
SKC1 : Ren et al (2005) isolated the SKC1 , a major
QTL for shoot K+ content, by map-based cloning, and
found that it encoded a member of HKT-type
transporters. They compared the SKC1 nucleotide
sequences between a salt-tolerant indica Nona Bokra
and a susceptible elite japonica Koshihikari allele, and
found six nucleotide substitutions in the coding region
which led to four amino-acid changes. Electro-
physiological analysis showed that the protein
encoded by SKC1 was specific transport proteins, but
not transported directly for K+, while the variation of
the content of K+ was caused by the competition of
Na +. The analysis indicated that the protein located on