IDENTIFICATION OF DIFFERENTIALLY EXPRESSED GENES IN RESPONSE TO MID-SEASON DROUGHT IN GROUNDNUT (Arachis hypogaea L.)
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Date
2017
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Acharya N.G. Ranga Agricultural University
Abstract
Drought is one of the major constraints in groundnut and governed by
many genes with small effects operating in a coordinating manner. The
present investigation was aimed for identification of differentially expressed
transcripts in response to midseason drought in groundnut. To this end, a
total of eleven genotypes viz., ICGV 07132, ICGV 07070, TCGS 1398,
TCGS 1157, TCGS 1073, TCGS 1173, MLTG 4, Narayani, Tirupati 1,
Kadiri 9 and Kadiri 6 were screened in pot culture for moisture stress
tolerance. Among the eleven genotypes, TCGS 1157 and MLTG 4
genotypes showed early recovery after reaching the permanent wilting point
and were grouped into moisture stress tolerant group. In contrast, Narayani
and Kadiri 6 were highly sensitive to moisture stress.
The field experiments were carried out at the research farm of
Regional Agricultural Research Station (RARS) and molecular analysis at
Genomics lab, Institute of Frontier Technology (IFT), RARS, Tirupati. The
contrasting genotypes for mid-season drought viz., MLTG 4 and TCGS
1157 (tolerant) and Narayani and Kadiri 6 (susceptible) were further
analyzed for morphological, physiological, biochemical and molecular
parameters submitted to midseason moisture stress (50-80 DAS) in the field
conditions.
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SPAD Chlorophyll Meter Reading (SCMR) and Specific Leaf Area
(SLA) were considered as surrogate traits for drought tolerance. The SPAD
Chlorophyll Meter Reading values were increased as moisture stress period
was increased upto 30 days in both drought tolerant and susceptible
groundnut genotypes studied. SCMR can be used as non-destructive
measure to estimate chlorophyll density while screening groundnut
genotypes for drought tolerance. SLA decreased significantly in drought
tolerant genotypes than in drought susceptible genotypes. Based on the SLA
values, groundnut genotypes can be clearly distinguished from the drought
susceptible genotypes.
The increased levels of proline under drought stress can be better
considered as drought stress indicator in groundnut. The accumulation of
proline was more as the moisture stress progressed up to 30 days in all
groundnut genotypes under the study.
The total chlorophyll content under moisture stress imposed in
groundnut genotypes initially was increased up to 70 DAS and declined at
80 DAS except for TCGS 1157. This was most probably due to prolonged
vegetative growth phase in TCGS 1157 (120 days duration) when compared
to MLTG 4, Narayani and Kadiri 6. To protect the cell from Reactive
Oxygen Species generated in photorespiration, both catalase and peroxidase
activities were increased in all the genotypes submitted to prolonged
moisture stress.
To unravel the molecular mechanisms conditioning drought
tolerance, transcriptome was analyzed in groundnut subjected to mid-season
stress (50-80DAS). To identify differentially expressed transcripts, cDNARAPD
analysis was carried out using total RNA collected from leaves under
well watered (control) and moisture stress situations at 10 (60 Days After
Sowing), 20 (70 Days After Sowing) and 30 (Days After Sowing) days.
Transcriptome was analyzed by cDNA-RAPD to identify
differentially expressed transcripts in groundnut subjected to mid-season
stress. cDNA-RAPD profiles with 35 RAPD markers resulted in a total of
823 reproducible differentially expressed transcripts in three regimes of
moisture stresses. Among the 823 differentially expressed transcripts, 523
transcripts exhibited qualitative difference while 300 transcripts displayed
quantitative differences in banding pattern of cDNA-RAPD profiles among
all the four genotypes.
Description
D5522
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