Molecular breeding for indica rice (Oryza sativa L.) genotypes with aerobic adaptation
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Date
2018
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CCSHAU
Abstract
In rice (Oryza sativa L.), HKR47 x MAS26, Pusa1121 x MAS25 and Pusa Basmati 1460 x MASARB25
derived F4, F5, F6, F7, F8, BC2F3, BC2F4 and BC2F5 populations were evaluated for various physio-morphological
(plant height, grain yield and yield components), grain quality (L/B ratio of grain and aroma) and root (root length,
biomass and thickness) traits under direct-seeded water-limited aerobic conditions in the field as well as net house
during 2014, 2015 and 2016 kharif seasons. While HKR47 and Pusa1121 and Pusa Basmati 1460, respectively, are
high yielding indica variety and premium Basmati rice varieties, MAS26, MAS25 and MASARB25 are
aerobic/drought tolerant indica varieties developed at UAS, Bangalore and IRRI, Manila, Philippines. These
aerobic rice varieties had 22 - 30 % higher yield and root biomass (15-20 %) than lowland indica/Basmati rice
varieties under direct-seeded aerobic conditions. The filial and backcross populations showed variation for both
agronomic and root traits. The grain yield/plant had positive correlation with root biomass in HKR47 x MAS26,
Pusa1121 x MAS25 derived populations. A total of 186/500 SSR markers well distributed on 12 rice
chromosomes, showed polymorphism in six parental rice genotypes; 83-87 polymorphic markers were used to
assess the genetic diversity in these populations. NTSYS-pc UPGMA tree cluster analysis and two-dimensional
PCA scaling showed that all the parental varieties were quite divergent and segregating populations were
interspersed between the two parental rice genotypes. Composite interval mapping analysis (WinQTL
Cartographer 2.5) using SSR databases of these populations led to the mapping of 81 QTL (LOD: 3.0-9.0 and R2%
5.3-53.4) for various traits promoting aerobic adaptation including grain yield/plant (21 QTL on chromosomes 1,
2, 5, 6, 8 and 10), plant height (13 QTL on chromosomes 1, 5, 6, 7, 10 and 11), effective number of tillers/plant
(16 QTL on chromosomes 1, 2, 5, 6, 7, 8, 10, 11 and 12), panicle length (15 QTL on chromosomes 1, 2, 4, 5, 6,
7, 8, 9 and 10), test grain weight (5 QTL on chromosomes 2, 4, 8 and 12) and dehusked grain L/B ratio(11
QTL on chromosomes 1, 2, 6, 7 and 8). Notably, 36 of these were large effect QTL with r2 value >20%. In
populations involving Basmati rice parent, plants had allelic profile at BAD2A locus like Basmati (585 and 257
bp) or non-Basmati (585 and 355 bp) parents or were heterozygous (585, 355 and 257 bp). Data on physiomorphological
traits and status at BAD2A locus were used to select promising aerobic rice genotypes in each
generation, advanced to next generation and evaluated further. Finally, in 2016, 23 plants were selected (five each
from HKR47 x MAS26 F6, F7 and BC2F5; four from Pusa1121 x MAS25 F8 and four from PB140 x MASARB25
F7 populations) based on field and net house evaluation data. Plant no. H/M26/F4/56-1-1 had highest grain
yield/plant (28.1 g; MAS26, 20.4±1.7) and root length (55.6 cm; MAS26, 46.1±3.4) followed by H/M26/F5/A15-
4-2 (25.8 g and 52.3 cm); H/M26/F4/56-1-1 had exceptionally higher fresh weight (33.3 g; MAS26, 13.7±1.4 g).
The selected plants possessed 3-9 favorable QTL/alleles in homozygous state and 1-29 in heterozygous state. Plant
H/M26/F4/56-1-2 had maximum (33) of favorable QTL/alleles either in homozygous (5) or heterozygous (28)
state. Preliminary replicated RBD yield trails revealed that 11/15 selected promising genotypesoutperformed the
respective check variety (HKR47, Pusa1121 or PB1460) under aerobic conditions. These genotypes will serve
as the novel material for the selection of stable water efficient aerobic indica/Basmati rice varieties. It will also
be interesting to investigate and confirm the role of these QTL in promoting aerobic adaptation.
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