Abstract
Ninety six parental lines including 48 CMS lines and 48 restorer lines were studied to
understand floral biology, yield contributing traits, and genetic diversity to identify best
lines of hybrid rice to enhance rice seed production. Different cyto-sources and fertility
restoration systems were also assessed to evaluate CMS and restorer lines. The research
was carried out during November 2016 to November 2019 in the research field of Hybrid
Rice Division and marker assisted laboratory of Genetic Resources and Seed Division of
Bangladesh Rice Research Institute (BRRI), Gazipur. Among the evaluated traits duration
and angle of open florets, panicle exsertion rate, stigma exsertion rate, outcrossing rate
and days to panicle emergence were played crucial roles for seed setting. Blooming
duration and filament length significantly influenced outcrossing. BRRI31R exhibited
best performance as a restorer line for yield contributing characters. In diversity
analysis, CMS and restorer lines were grouped into five clusters based on morphology.
Clusters remains in maximum divergence were also genetically distant for relevant
traits. Cluster IV possessed maximum CMS lines of 18. Similarly, Cluster III contained
14 restorer lines which was highest. Four restorer lines BRRI10R, BRRI15R, BRRI20R and
BRRI31R paired with five CMS lines IR75608A, IR79156A, BRRI7A, BRRI10A and
BRRI11A, produced outstanding rice hybrids. In marker assessment, 56 SSR markers
identified 178 and 171 polymorphic alleles in 48 CMS and 48 restorer lines respectively.
The highest PIC was observed for the primer of RM591 (0.7452) followed by RM228
(0.67) and RM16. All the loci except the three primers (RM591, RM228 and RM16)
showed low PIC value (<0.60) of CMS lines and the highest PIC values were observed
for the primer of RM307 (0.71) followed by RM252 (0.70). All the loci except the six
primer (RM145, RM252, RM307, RM133, RM206 and RM209) showed low PIC value
(<0.60) of restorer lines. From diversity analysis, 10 CMS lines and 16 restorer lines
could be selected to produce competitive rice hybrids. The hybrid BRRI7A/BRRI31R
gave the highest seed yield 2.69 t ha-1 in the Boro 2017-18 season, which was
significantly higher than rest hybrids in this study. The study which might be due to the
presence of higher outcrossing rate, panicle exsertion rate and stigma exsertion rate in
this parental combination that the rest. For hybrid seed production twelve rows of CMS
line and two rows of restorer lines with the spacing of 15x15 cm between CMS lines
found to be the optimum row-ratio and spacing that could give higher Fâ seed yield,
significantly higher tiller numbers, highest panicle exsertion rate and outcrossing rate
that can enhance better seed yield. The highest seed yield (2.51 t ha-1) was found when
GA3 level was 250 g ha-1 with 4 equal doses of GA3 application interacted favorably in
producing seed yield of BRRI7A/BRRI31R. The effect of growth regulators on grain
yield showed that it was significantly increase with a range of 1.61 to 2.70 t ha-1. The
treatment T18 i.e., GA3 (220 g) provided highest increase in seed yield (2.70 t ha-1) than
rest treatment combinations of hybrid seed production.