BIOCHEMICAL AND MOLECULAR ANALYSIS OF DROUGHT TOLERANT AND SUSCEPTIBLE CULTIVARS OF SORGHUM
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Date
2007
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Mahatma Phule Krishi Vidyapeeth, Rahuri
Abstract
The present investigation was carried out to study the
proline metabolism in response to osmotic stress and RAPD
analysis of genomic DNA with 18 different decamer primers in six
drought tolerant and six susceptible sorghum cultivars.
The seeds of these cultivars were germinated on petriplates
in duplicate sets, for 5 days in incubator at 27±2°C under normal
conditions. The osmotic stress of -1.0 MPa was applied to
seedlings in one set with PEG 6000 (29.57 %) solution. Roots
were harvested after another 5 days of grown under stress and
analyzed for changes in proline content, P5CS activity and
soluble proteins. The genomic DNA was extracted from 15-days
old whole seedlings grown under normal condition, purified and
subjected to RAPD amplifications using 18 different decamer
primers Application of osmotic stress was found to increase the
mean proline accumulation from 2.33 to 17.43 mmoles g-1 root
tissues i.e. about 8 folds in tolerant types. Under similar
conditions, the mean proline accumulation was found to range
from 1.83 to 7.51 mmoles g-1 root tissues i.e. 4 folds in
susceptible cultivars. The mean P5CS activity was found to
increase from 0.16 to 0.54 mmoles g-glutamyl hydroxymate g-1
tissues min-1 (4 folds) in tolerant types while it was found to
increase from 0.16 to 0.28 mmoles of g-glutamyl hydroxymate g-1
tissues min-1 (2 folds) in susceptible cultivars. Similarly,
application of osmotic stress was also found to increase the root
soluble protein contents by about 3 folds in tolerant cultivars and
by about 2 folds in susceptible cultivars. These results indicated
that, an increased proline accumulation due to stress is a good
indicator of drought tolerance in sorghum. An increased P5CS
activity during stress indicated the fresh biosynthesis of proline
in roots during stress. An increase of soluble proteins due to
stress supported the increased enzyme synthesis and least
protein degradation during stress conditions.
RAPD analysis of genomic DNA of 12 cultivars showed
22.22 to 90.00 per cent polymorphism with 18 different primers.
Among the primers tested, OPC-19 showed one distinct amplicon
of 1.38 Kb size and primer OPE-03 indicated one distinct band of
0.29 Kb size in tolerant cultivars. Primers OPE-09 and OPA-07
exhibited distinct bands of 0.92 Kb and 0.70 Kb size respectively
in some susceptible types.
These distinct bands can be used in designing specific
primers for further screening of segregating populations.
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