Near isogenic F2
(
NIF2) population frequently
developed by conventional backcross has dramatically
contributed to QTL identification in plants.
Developing such a NIF2
population is time-consuming.
Thus, it is urgent to rapidly produce a NIF2
population
for QTL cloning. Here, we proposed a rapid
QTL cloning strategy by generating a Pseudo-near
isogenic F2
population (Pseudo-NIF2), which segregates
at the target QTL but is fixed at other QTLs
for the target trait. Nineteen QTLs for GL, GW, and TGW were detected in the F2
population from the
cross between Zhenshan 97 and Egy316. To verify
the efficiency of Pseudo-NIF2 in QTL quick cloning,
the novel moderate QTL qGL10.1 which explained
9.1% and 5.6% of grain length variation in F2
and F2:
3
populations was taken as an example. An F2
plant
(
F2-120), which segregated at qGL10.1 but fixed at
other 8 QTLs for grain length, was screened to generate
a Pseudo-NIF2 population by selfing cross. In
the Pseudo-NIF2 population, the segregation ratio of
plants with long grains to short grains fits 3:1, indicating
that one gene controlled the variation of grain
length. Based on the Pseudo-NIF2 and its progeny,
qGL10.1 was fine mapped to a 19.3-kb region, where
a gene OsMADS56 was verified as the candidate by
functional polymorphism between parental alleles.
Pseudo-NIF2 strategy is a rapid way for QTL cloning,
which saves 3 to 4 cropping seasons compared to the
conventional way. Applying the method for cloning
QTL with moderate or major effects is promising.