SELECTIVE LINE GENOTYPING FOR IDENTIFICATION OF MARKERS ASSOCIATED WITH HEAT TOLERANCE IN RICE (Oryza sativa L.)
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Date
2017
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Acharya N.G. Ranga Agricultural University
Abstract
Due to global warming and quickening industrialization environment is
changing day by day and heat stress has become a major challenge for sustained
production of rice. Rice is highly sensitive to heat stress during all growth stages,
which will reduce the yield and create great losses. Production levels are decreasing
gradually due to high temperature conditions. Hence, the present investigation was
carried out to identify rice genotypes which can withstand high temperature
conditions by employing Selective Line Genotyping approach.
A set of 74 genotypes were tested for heat tolerance under laboratory
conditions employing Temperature Induction Response (TIR) technique with three
temperature conditions viz. Control at room temperature, Sub-lethal gradual exposure
to 38˚C -55˚C range and Lethal at 55˚C. Based on survival percentage (SP), relative
root length, and relative shoot length measured under sub-lethal conditions over
control, 14 genotypes were selected each under tolerant and sensitive classes. The
genotypes under tolerant class fell between 80-100% survivability.
Of 14 tolerant genotypes, two genotypes viz. FR13A and Swarna Sub1A
showed 100% survivability and were highly out performed to check genotypes in
relative root length (62.53% and 47.56%, respectively) and shoot length (106.20%
and 40.74%, respectively), in comparison to known tolerant genotypes. Next to
survival percentage, root length plays an important role for selecting genotypes. In our
study Maximum root length fell in the range of 4.8 cm - 10.74 cm and maximum RRL
was observed for BPT1235 (82.54%). Also when it comes to shoot length, highest
shoot length was recorded in BPT1235 which is about 11.75cm.
Based on the survival percentage (SP), RRL and RSL of genotypes, a total of
14 genotypes under each class viz. heat tolerant and heat sensitive classes were
selected and used for molecular studies employing selective line genotyping approach
(SLG). Under selective line genotyping approach, the selected tolerant and sensitive
sets were genotyped with 51 SSR and genic markers. Out of all the 51 markers which
were genotyped, the markers RM17270, RM16216, RM5687 and TTC/TTM gave
polymorphic alleles, whereas 92% the markers couldn’t distinguish tolerant set from
sensitive and as well among reported tolerant genotypes (N22, Dular and
Nipponbare).
In our study, the alleles generated by different polymorphic markers were not
clearly distinguished the tolerant set from sensitive set of genotypes. Among the
reported genotypes also the allele sizes were varied except for the marker TTC/TTM,
as they are from different sub groups of rice. N22 and Dular comes under Aus group,
whereas Nipponbare comes under japonica group.
From the experiment, we have concluded that both heat stress tolerant
genotypes FR13A and SwarnaSub1A can be used as donor sources for heat tolerance
because these genotypes proved themselves to be good performers under sublethal
conditions, also their amplification pattern with well reported loci RM17270 is similar
to checks Dular and Nipponbare. Although, the other three markers are not much
informative in the current study, to distinguish the tolerant group from sensitive
group, they are reported to be linked to heat tolerance by different research groups.
Thus, our study has unveiled valuable markers (regions) and genotypes in developing
alternative donor sources in indica rice, rather original aus and japonica group, where
they originally identified, to use them in heat tolerance breeding programmes for
better yields.
Put together the involvement of small set of phenotyping panel and use of
extremely core set of genotyping panel for SLG that generated most relevant
association of potent markers along with identified donors comparable to QTL
mapping results. Further, the diverse allele pattern exhibited by genotypes alike large
association panel, additional knowhow of the degree of association of a locus makes
the SLG technique to be challenged as greatly powerful.
Description
D5523
Keywords
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