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Rice Genomics and Genetics 2012, Vol.3, No.7, 39
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49
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45
Continuing table 2
Parents
Population Traits
Number of QTL
(Chromosome)
Variance
explained (%)
Reference
Root Na
+
concentration
1 (9)
16.7
Shoot Na
+
total quantity
1 (7)
16.1
Root Na
+
total quantity
1 (1)
12.4
Jiucaiqing/IR36
F
2
Salt damage level
3 (1, 5, 9)
6.7~14.3
Yao et al., 2002
Ratio of root Na
+
/ root K
+
2 (2, 6)
7.9~19.3
Fresh weight of stem and
leaf
2 (8, 9)
9.3~9.9
Dry weight of stem and
leaf
2 (8, 9)
7.5~11.5
Root length
2 (4, 5)
6.4~7.4
Na
+
content
2 (4, 7)
8.9~9.8
K
+
content
2
（
4, 5
）
6.4~8.8
H359/Acc 8558
RIL
Na
+
content in seedling
stage
13 (1, 1, 1, 2, 2, 2, 5,
5, 6, 7, 7, 12, 12)
1.68~45.39
Wang et al., 2007
DST
: A drought and salt tolerance
(dst)
mutant derived
from a
japonica
cultivar Zhonghua 11 with
ethylmethanesulfonate (EMS) treatment was identified,
and the
DST
was cloned by the map-based cloning.
DST
encoded a previously unknown zinc finger
transcription factor that negatively regulated stomatal
closure by direct modulation of genes related to H
2
O
2
homeostasis, which identified a novel pathway for the
signal transduction of DST-mediated H
2
O
2
-induced
stomatal closure. The assessment of the two amino
acid substitutions (N69, A162) in the
dst
mutant
showed that the N69 of
DST
was required for
transcriptional activation. As a negative regulator,
DST
could directly down-regulated the expression of genes
related to H
2
O
2
metabolism when it lost the function,
making the ability of removing H
2
O
2
decrease, the
accumulation of H
2
O
2
in guard cell increase, then
increases the stomata closure and reduces the water
evaporation, consequently enhanced the salt tolerance
of rice. Moreover, they found that the down-regulation
of
DST
did not affect rice grain yield, which facilitated
molecular breeding efforts to improve drought and salt
tolerance in staple crops (Huang et al., 2009).
4 Breeding of salt tolerance rice
We have obtained significant progress on the research
of the salt tolerance mechanism, the identification of
the salt tolerant germplasm and the study of relevant
molecular mechanism of rice, which will lay the
foundation for the breeding of salt tolerance rice.
4.1 Direct using or conventional breeding of the
salt tolerance germplasm of rice
To improve the salt tolerance of rice is not only to
improve the yield, but also to expand the area of the
saline soil. Breeders (Zhang et al., 2004; Yin et al.,
2002) obtained a series of rice varieties with the
resistance to different concentrations of salt using the
known salt tolerance germplasm or through the
conventional breeding, and the salt tolerance rice
varieties like Liaoyan No.2, Dongnong 363, Changbai
No. 6 and 7, Zhaiyeqing 8 and Tesanai No.2 had
applied in production. In the slight saline soil, IRRI
developed 8 t/hm
2
of the production by using the salt
tolerance variety without any improvement measures
to the soil (Zhang et al., 2004).
4.2 Breeding of the salt tolerance of transgenic rice
Li et al (2005, Chinese Science Bulletin, 8: 613-617))
transferred the
HAL2
gene (
RHL
) to the
japonica
Hejiang 19 with the via
Agrobacterium
-mediated
transformation, the salt tolerance of the positive plants