Molecular Plant Breeding 2016, Vol.7, No.33, 1
-
15
6
In this study, the transfer of the durable blast resistance gene,
Pi40
into two Turkish elite cultivars using
marker-assisted backcross breeding has been considered as an effective approach. Several blast resistance genes
including
Pi-b
,
Pi-k
,
Pi-i
,
Pi-z
,
and
Pi-ta
, have also been introgressed in different breeding programs using similar
approach (Miah et al., 2013). In case of
Pi40
, an earlier work also introgressed the gene in two japonica cultivars,
Jinbubyeo and Junambyeo (Suh et al., 2009). Inter-varietal cross progenies were produced using Osmancık-97 and
Halilbey as recurrent parents and transferred the
Pi40
gene from a japonica genetic background. BC
3
F
5.6
and
BC
4
F
5
.
6
progenies were developed by repeated backcrossing to the respective recurrent parents after conducting
foreground selection for the target
Pi40
gene. Further
confirmation of the selected plants at each backcross
generation has been carried out by blast disease evaluation in natural field and spray inoculation conditions. This
approach has enhanced the selection efficiency for the target blast resistance gene at a shortest time possible as it
has been shown in case of transferring brown planthopper (BPH) resistance gene,
Bph18
and submergence
tolerance gene,
Sub1
in rice (Neeraja et al., 2007; Suh et al., 2011).
The
Pi40
gene conferred blast resistance to virulent strains in the field as well as selected virulent blast strains in
the glasshouse. ABLs tested showed resistance to majority of the blast isolates used. However, some ABLs (ABL2,
ABL3, and ABL4) showed susceptibility to strain P06-06 even though the donor and recurrent parents were
resistant. This result suggested the loss of resistance gene during meiotic recombination and it was similar to the
findings of Fu et al., (2012). The identification of the
Pi40
gene in the selected blast resistant plants from different
backcross generations by foreground analysis revealed the power of the DNA marker, 9871.T7E2b which has
been designed from NBS-LRR motif sequences (Jeung et al., 2007). This study not only revealed the successful
transfer of blast resistance gene into Osmancık-97 and Halilbey but also confirmed tight linkage between the
Pi40
gene specific marker and blast resistance phenotype. Interestingly, the early generation lines selected for blast
resistance expresses resistance to blast races/strains in Turkey in a preliminary field test. Also, further testing of
advanced backcross generation progenies at several locations in Turkey revealed that all ABLs we selected
confirmed resistance to blast. This study will enable the isolation of promising breeding lines for their adaptation
and cultivar development.
The major target in this study was the introgression of the
Pi40
gene from the donor parent
(IR83260-1-1-1-5-B-3-1-2-B) into the genomes of Osmancık-97 and Halilbey. The chromosome segment
containing the
Pi40
gene was introduced and the improved ABLs of BC generations contained limited donor
derived chromosome segments in the recurrent parent background genome. Conventional molecular techniques in
breeding employ the separation of PCR amplicons in agarose or polyacrylamide gels and subsequent visualization
in gel documentation systems. These steps are not just laborious but more importantly, cost-ineffective
(Ramkumar et al., 2015). The advent of advances in molecular breeding which include SNP genotyping
technologies and automated capillary electrophoresis systems has the potential to answer these problems.
Automation using capillary electrophoresis can also potentially lower the cost and time utilized during gel
electrophoresis preparations. To demonstrate the applicability of these new technologies, ABLs, RPs, and DP were
SNP genotyped using Illumina 6K Infinium SNP Chip. PCR amplicons from the parents and ABLs were also run
in an automated capillary electrophoresis system using Fragment Analyzer. A similar strategy was performed
using the
Pi2
gene. Elite thermo-sensitive genic male sterile lines were introgressed with
Pi2
using molecular
breeding approach (Jiang et al., 2015). A whole genome SNP array similar to what is used in this study was also
utilized for background genotyping. RP genome recovery computed in their study was close to the genome
recoveries of ABLs produced in this study. In one of the ABLs, it was also shown that most chromosomes were
