Abstract
In coastal regions, both salinity and submergence stress alternatively or
simultaneously become severe constrain to rice cultivation due to climate
changes. This situation necessitates the research of combined to salinity and
submergence tolerant rice varieties. The study was designed to develop suitable
salinity-submergence tolerant high yielding varieties at Bangladesh Institute of
Nuclear Agriculture (BINA), BAU campus, Mymensingh-2202 through
introgression of submergence tolerant QTL, (Sub1) into submergence sensitive
but salt tolerant variety, Binadhan-10 and salt tolerant QTL, (Saltol) into salinity
sensitive but submergence tolerant variety Binadhan-11. The dual tolerant
(Saltol-Sub1) donor lines RC-251, RC-222, RC-291, RC-249, RC-193 and RC-292
were selected from 14 advanced lines collected from International Rice Research
Institute (IRRI) through three separate screening experiments. The advanced
lines with other check varieties screened at hydroponic culture with 12 dSm-1 of
Electrical Conductivity (EC) at the seedling stage. Another screening program
was conducted for submergence tolerance at 21 days under 40 cm complete submergence and the last screening experiment for salinity-submergence
tolerance at 21 days under 40 cm complete submergence at 12 dS/m salinized
condition. The SSRs (simple sequence repeats) namely RM493, RM10793,
RM7075, RM490 and AP3206 were accomplished to identify Saltol region and
Sub1 linked markers Sub1BC2, RM5688, RM336, RM23662, RM216 and SC3
were used to detect donor segments in Binadhan-10 and Binadhan-11. Final
genotyping was done at BC2F2 generation of all combinations. From the
combinations Binadhan-10×RC-251, Binadhan-11×RC-193, Binadhan-10×RC222, Binadhan-10×RC-291, Binadhan-10×RC-249 and Binadhan-11×RC-292, a
total of 45, 48, 10, 8, 10 and 12 as heterozygous NILs were identified
respectively at both loci (Saltol and Sub1) through MAS. The best individuals of
two major combinations (Binadhan-10×RC-251 and Binadhan-11×RC-193) with
target loci (Saltol-Sub1) were selected through GGT analysis and phenotypic evaluation. A correlation coefficient distance was constructed through UPGMА
method based on 10 morphological traits. Based on the cluster analysis, 17 NILs
were grouped with the recurrent parent Binadhan-10 with 95.19% similarities.
On the other hand, the recurrent parent, Binadhan-11 along with 33 NILS were
grouped with 99.55% similarities. The individuals of BC2F2 generation with Saltol-Sub1 loci, selected through GGT analysis were selfed to obtain BC2F3 progenies. Finally, 10 and 24 NILs with Binadhan-10 and Binadhan-11
background respectively, were selected. The new versions of Binadhan-10 and
Binadhan-11 with Saltol-Sub1 loci, can be exploited for further gene mapping in
order to develop potential dual tolerant varieties to elevate and sustain rice
production and thereby improve livelihood of coastal farmers.