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Molecular Plant Breeding 2010, Vol.1 No.1
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traits. These quantitative traits generally controlled by
quantitative trait loci that shortly called as QTL. QTL
analysis allows us to identify chromosome loci
conferring the complex traits (Wade et al., 2001). In
the past decade, there are large of numbers of QTLs in
cultivated rice (
Oryza sativa
) cultivars identified
(Xiao et al., 1998; Xiong et al., 1999; Cai et al., 2002).
The introgression of novel alleles from wild
germplasm is one effective approach for further
improving of agronomic traits, which have been
successfully used in cultivated rice breeding program
as reported in QTL mapping studies (Xiao et al., 1998;
Aluko et al., 2004; Moncada et al., 2001; Septiningsih
et al., 2003a; Tian et al., 2006). Studies also indicated
that wild rice species usually show their agronomic
characters inferior to that of cultivated species,
whereas these wild rice species definitely contain
much more favorable alleles that might be important
for cultivated crops (Frey et al., 1983). Although the
wild rice germplasms were successfully utilized in
rice breeding program to some extent, it becomes
much difficult to employ these favorable traits due to
lots of linking inferior characters. For example,
adverse factors (unfavorable agricultural characters
and undesirable linked genes, overrepresentativeness
of wild rice genes in balanced population, and
negative genetic linkage drag, and so on) have fatal
influenced on the utilization of wild rice germplasm,
in particular to find favorable genes from wild rice
(DeVicente et al., 1993; Eshed et al., 1994).
Advanced backcross QTL (AB-QTL) analysis is a
known approach to find elite genes in wild rice.
AB-QTL analysis has been successfully applied in
detecting and transferring QTLs from un-adapted
germplasm into advanced breeding lines in various
plant species (Xiao et al., 1998; Tanksley et al., 1996;
Bernacchi et al., 1998a; Bernacchi et al., 1998b; Xiao
et al., 1996).
In this research, we developed an interspecific
advanced backcross population and planted at two
different locations in two continuous years. The
recurrent parent employed is an elite cultivar called
‘Yuexiangzhan’ in Chinese and the donor parent is a
wild rice germplsam (O.
rufipogon L
) deposited in
germplasm bank with accession No. G52
-
9. The
objectives of this study were to evaluate the
agronomic performance and yield component of the
advanced backcross populations based on the analysis
of genotypic and phenotypic data. In addition,
quantitative trait loci conferring some interesting traits
were identified by using generated introgression lines
(ILs) and near-isogenic lines (NILs) in these studies.
1 Results
1.1 Trait phenotypic scores and statistic analysis
We phenotyped ten yield related traits and calculated
the values of mean, minimum, maximum, and
coefficient of variation listed in Table 1. The results
showed that differences in variance for all traits were
highly significant (P<0.01 or P<0.001) based on the
t-test. The phenotypic analysis of the traits in the 245
backcross progenies showed that the frequency
distribution of all tested traits fit approximately
normal distribution (histograms not shown). As
expected for an interspecific cross, distribution of
phenotypic vales in progeny showed bi-directional
deflective separation for all traits. Most of the trait
values of the 245 backcross families have higher than
that of the recurrent parent, Yuexiangzhan. According
to the statistical data, there are about 33.20% of the
BC
3
F
3
lines with better traits than that of the wild type
Yuexiangzhan (BC
3
F
3
data not shown).
1.2 Correlations among the yield related traits
Phenotypic correlations were conducted among the
evaluated yield-related traits based on the means. The
traits with highest significant positive correlation were
found between grain number per panicle and grain
number per plant (Pearson correlation coefficient, 0.659,
P<0.001), Whereas the traits with significant negative
correlation were found between 1000
-
grain weight
and Spikelet density (Pearson correlation coefficient,
-
0.235, P<0.001).All of the Traits with their Pearson
correlation coefficient are listed in table two.
1.3 SSR marker polymorphisms
Polymorphism is recognizes as a measurement for
genetic diversities between the breeding parents. In this
study total of 551 SSR markers were used to detect the
polymorphism between the parents, which are 162
SSRs to show polymorphism (29.4%). The results show
that the rate of polymorphism is much lower than that