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Rice Genomics and Genetics 2012, Vol.3, No.3, 13
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that it was viable for detection the
Pi1
gene by SSR
marker, and the landraces with small fragment were
not carrying
Pi1
gene, while the landraces with large
fragment were harboring
Pi1
gene.
Base on PCR detection, there were 64 carrying
Pi1
gene (36.99%) among 173 landraces. The distribution
of
Pi1
in japonica and indic rice were difference, 33 of
102 indica rice were holding
Pi1
gene (32.35%), 31 of
71 japonica rice carrying
Pi1
gene (43.66%). The
results showed that indica rice harboring
Pi1
genes
were higher than that of japonica rice.
1.2 The distribution of landraces holding
Pi1
gene
in rice-growing-region of Yunnan Province
The
Pi1
gene is distributed in all rice growing regions
(Table 1). The frequency of landrace holding
Pi1
gene
in paddy-upland rice region in South marginal of
Yunnan, single and or double indica cropping region
in south of Yunnan, single indica and or japonica
cropping region in center of Yunnan, japonica cropping
region in northeast of Yunnan and japonica cropping
region in northwest highland of Yunnan, was 41.03%,
32.69%, 35.29%, 35.29% and 33.33%, respectively.
The frequency of landrace carrying
Pi1
gene in
paddy-upland rice region in Southen marginal was
higher than the remained rice-growing-regions, and
the frequency of
Pi1
gene were below 36.99% in other
regions. The 64 landrace with
Pi1
were distributed in
29 counties of 11 prefectures, and distributed widely.
There were not detected the
Pi1
gene in landraces
from Dali, Wenshan, and other 17 counties (cities),
which may be due to less materials for test. The
frequency of
Pi1
in each county (more than four
landraces) was quite different. The first main different
was the frequency of landraces carrying
Pi1
in some
of counties were higher, but in some of counties were
low in the same prefecture. Example, Lianghe County
(6 test materials) of Baoshan City, Wenshan County (4
test materials) of Guangnan prefecture, Yanjin County
(4 tested material) of Zhaotong City, all landraces not
carrying the
Pi1
gene. However, the Pingbian county
of Red River state (4 test materials, the frequency was
100%), Yongde county of Lincang city (5 test
materials, frequency was 60%) and Gengma county (5
test materials, frequency was 60%), those counties
have a higher frequency. The second different was the
geographical proximity, but large differences in the
frequency of
Pi1
. Such as Jiangcheng county and
Mojiang county were proximity in geographical, but
the frequency of
Pi1
were 41.67% and 20.83%,
respectively. Similar results in Tengchong county
(frequency was 50%) and Lianghe county (frequency
was 0%), the ecological conditions are similar in
relative county, but the frequency of
Pi1
gene was
large different. The results showed that
Pi1
gene were
broader distribution in Yunnan, and showed irregular
distribution.
2 Discussion
Ancient landraces and rice blast fungus has a long
coexistence history, and the specific interaction
between the rice blast fungus and rice were according
to the
“
gene for gene
”
relationship. Landrace
resources are the results of a long-term co-evolution
between varieties resources and rice blast fungus, and
rice blast fungus played natural selection role in the
process of long-term cultivation. The distribution of
resistance genes and the rice blast were closely related.
This study showed that
Pi1
gene distributed in 29
counties and 11 prefectures of Yunnan Province, but
we haven’t found the
Pi1
gene in landraces collected
from remaining 17 counties (cities) which may be due
to the small test materials in those regions, if increase
large number of test materials, may be can detected it
in more counties, those indicated that
Pi1
gene was
widely distribution in Yunnan Province. It is relative
between the distribution of
Pi1
gene and rice blast
races.
Pi1
gene can be employed in indica and
japonica cropping region (Li et al., 2005). This result
also showed that the analysis of the distribution of
resistance genes in ancient populations of landraces
can direct the rice blast resistance breeding program
and rice blast control by genetic diversity.
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