MSc

The project entitled “Evaluation of sesame genotypes for tolerance to
Waterlogging" was undertaken with an objective to identify sesame genotypes
which are tolerant to excess soil moisture conditions, to elucidate the mechanism
for tolerance and to find out the selection index for identification of tolerant
genotypes. Two experiments viz. pot culture and field experiments were
conducted during 2014-16 at Onattukara Regional Agricultural Research Station,
Kayamkulam.
Thirty genotypes were screened at seedling stage (20 days after sowing)
by pot culture experiment to identify tolerant types for excess soil moisture by
imposing flooding for 24 hours, 48 hours and 72 hours duration. All the genotypes
survived 24 h and 48 h of waterlogging while 17 genotypes alone survived 72 h of
waterlogging. Observations of the genotypes which survived 72 h of flooding
were recorded and the results showed that the genotypes differed significantly for
the characters under study. Ten genotypes viz. Ayali, Sesamum malabaricum,
TKG 22, OSC 207, Thilak, Thilarani, GT 10, SV 2, TKG 308 and Rama which
recorded the highest survival percentage were selected for field experiment
In the field experiment flooding was imposed for 72 h duration and
biometrical characters were recorded and statistically analysed. All the characters
showed significant difference among the genotypes. Among the ten genotypes
highest yield per plant was recorded by the local variety, Ayali (7.46g) and lowest
by Sesamum malabaricum (2.92g). Oil content was highest for Thilak (48.6 %)
and lowest for wild species Sesamum malabaricum (32.5%).
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To elucidate the mechanism for flood tolerance, anatomical and
biochemical studies were conducted. Anatomical study revealed that there was
significant formation of aerenchymatous tissue in the flood tolerant genotypes
compared to the control. In the biochemical study, the total chlorophyll content
was highest for Ayali (0.56 mg g -1 ) and lowest for SV 2 (0.20 mg g -1 ). The total
soluble protein was highest for SV 2 (95.2 mg g -1 ) and lowest for Sesamum
malabaricum (28.2 mg g -1 ). Proline content was highest for Sesamummalabaricum (2.41 mg g -1 ) and lowest for TKG 22 (0.97 mg g -1 ). Superoxide
dismutase (SOD) was highest for Sesamum malabaricum (1.89 mg g -1 ) and lowest
for SV 2 (0.29 mg g -1 ). Phenol content was highest for Sesamum malabaricum
(0.25 mg g -1 ) and lowest for Thilak (0.03 mg g -1 ).
Phenotypic coefficient of variation (34.8), genotypic coefficient of
variation (34.6) and genetic advance (88.1) were highest for yield per plot.
Heritability was highest for number of days to maturity (99.9 %.). There was a
strong positive genotypic (0.92) and phenotypic correlations (0.95) between
number of seeds per capsule and yield per plant. There was a negative correlation
between oil content and days to maturity (-0.80). In path analysis direct effect
number of capsules per plant recorded highest positive direct effect (0.488) with
yield per plant. Plant height registered a positive indirect effect through number of
capsules per plant (0.435). Ten genotypes were grouped in to five clusters by
genetic divergence analysis. There was maximum intra cluster distance for cluster
1 (1424.43) and maximum inter cluster distance for cluster II and cluster V
(7739.41). Selection indices were calculated on the basis of all the biometric
observations and it was highest for Ayali (1319.65) followed by Rama (1208.48)
and OSC 207 (1205.30).
In the present study, Sesamum malabaricum, a wild species and Ayali, a
local cultivar of Sesamum indicum were identified to have tolerance to excess
moisture conditions. The production of aerenchymatous tissue and comprehensive
actions of proline, SOD and phenol production gave excess moisture tolerance in
plants. These tolerant genotypes can be used as parents for further breeding
programmes.