MSc

The present study an “Oxidative stress and protein profiling in cassava
(Manihot esculenta CRANTZ) under abiotic stresses” was conducted during the
period 2014- 2015 in the Division of Crop Production, CTCRI (Central Tuber
Crop Research Institute) Thiruvananthapuram. The objective of the study was to
elict information on the antioxidative enzyme activity, protein profiling, growth
parameter and yield parameter of four varieties / genotypes of cassava under
irrigated, high temperatures stress (40 o C ±2 o C) and water deficit stress (WDS)
conditions and identify marker physiological parameter which can be used for
identifying / developing cassava varieties for tolerance to abiotic stress conditions.
The study indicated that the plant height of four different cassava varieties were
not significantly affected by heat and WDS. The leaf production of four different
cassava varieties were significantly affected by both heat and water stress, and the
same was maximum in the case of water stress. The leaf retention of four varieties
/ genotypes were differentially affected by both heat and water stress. There was
negligible difference in yield parameters between stress and control condition.
However, there was significant difference was yield observed for parameters
among the four varieties. The effect of abiotic stress on various physiological
parameters like relative water content, chlorophyll and carotenoid content showed
significant difference in control plants. Among the given WDS and HTS
treatments, the chlorophyll and carotenoid content decreased in all the four
varieties. Chlorophyll and carotenoid content were significantly reduced in plants
exposed to HTS.
Relative water content of leaves varied under both WDS and HTS
conditions. A higher RWC was observed in plants exposed to HTS condition
compared to WDS condition. Total soluble protein content of leaf and tuber was
found to be lower in plants exposed to stress conditions. Total soluble protein in
tuber forming roots had increased under HTS conditions. Proline status of plants
under stress conditions followed an increasing trend compared to stress
conditions. The effect of abiotic stress on various enzymatic antioxidants such asGlutathione Reductase (GR), Superoxide Dusmutase (SOD), Catalase (CAT) and
Ascorbate Peroxidase (APX) were studied. Among the four different cassava
varieties. Kunguma rose showed maximum GR activity showed an increasing
trend in WDS compared to HTS and stress free conditions. Catalase activity of
four varieties of cassava plant varied among different stress condition (WDS and
HTS) compared to control. The catalase activity was significantly reduced due to
stress conditions and. SOD activity increased under stress conditions. The
ascorbate peroxidase (APX) activities had significant variation in WDS and HTS
compared to control. The AA content in cassava leaves was negligible or below
detectable amount under both control and stress conditions.
Under HTS condition GR activity increased in H-165 and Sree Athulya
alone whereas all the four varieties showed increase GR activity under WDS.
Kunguma rose showed maximum SOD activity in HTS whereas Sree Athulya had
highest SOD activity in WDS. APX activity was high in all the varieties under
HTS. From the present study it is inferred that GR can be used as a biochemical
marker for developing WDS tolerant varieties as it showed consistent changes
under both WDS and HTS. APX activity can be used as a marker for identifying
HTS tolerant varieties. Detailed molecular biochemical and physiological study
will be necessary using different varieties for getting appropriate activities as the
marker to screen abiotic stress tolerant varieties.