Genes controlling the regeneration ability of cultured cells have been
detected as quantitative trait loci (QTLs). In rice, five QTLs associated
with the regeneration ability of seed callus have been detected and tentatively
named as follows:qRg1 for chromosome 1, qRg2 for chromosome
2, and qRg4a, qRg4b and qRg4c for chromosome 4 (Taguchi-Shiobara
et al. 1997). In barley, a locus on chromosome 2H conferring the
regeneration ability of callus derived from immature embryo has been found
and named Shd1 (Komatsuda et al. 1995). Using several markers
dispersed on the whole barley genome, four QTLs were found and named Qsr1,
Qsr2 Qsr3 and Qsr4 (Mano et al. 1996). The
correspondence between barley QTL and rice QTL was examined, because these
diploid grass species have a simple genome structure without genome duplication.
RFLP markers linked to the five barley QTLs controlling the regeneration
ability of cultured cells (Komatsuda et al. 1995, Mano et al.
1996) were located in rice linkage map described by Lin et al.
(1998). The rice linkage map was constructed using 98 BC1F5
lines derived from two varieties, Nipponbare and Kasalath. To cover the
putative region of the barley QTLs, 26 barley markers were selected from
Mano et al. (1996). Three markers, including one of the aforementioned
26 markers, were selected from Komatsuda et al. (1995).
Twelve of the 28 probes studied showed polymorphic bands between Nipponbare
and Kasalath. These were mapped to 16 locations on the rice linkage map
(data not shown). Some of the probes that showed multiple polymorphic
bands were located on two or three loci. Two of the 16 barley markers,
MWG865 linked to barley Qsr1 and Shd1 on chromosome 2H,
and ABC171 linked to Qsr2 on chromosome 3H, were located near rice
qRg1 on chromosome 1 (Fig.1). MWG503, CDO588 and ABG014, linked
to barley Qsr1 and Shd1, were located near rice qRg4b
on chromosome 4. CDO588 was also located near rice qRg2 on chromosome
2. The order of ABG014-CDO588-MWG503 was conserved between barley chromosome
2H and rice chromosome 4. The order of the other markers was not conserved
between rice and barley (data not shown).
Our results suggest that barley Qsr1 and Shd1, and rice
qRg4b originated from the same chromosomal block of ancestral species
of grass. This agrees with earlier findings that the long arm of barley
2H shares a conserved segment with rice chromosome 4 (Van Deynze et
al 1995). Further genetic analysis is needed to clarify the precise
location and function of each QTL.
We thank Drs. A. Kleinhofs, Washington State University, USA., M. Sorrells,
Cornell University, USA and A. Graner, Institute for Resistance Genetics,
Germany, for providing us the probes. Thanks are also due to Drs. S. Y.
Lin, M. Yano and T. Sasaki, Rice Genome Research Program, and Dr. Mano,
National Institute of Agrobiological Sciences, for map construction.
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