Amrutha Vijayakumar
Response mechanisms induced by exposure to high temperature in tomato genotypes and development of suitable management strategies for enhancing thermo- tolerance - Vellayani Department of Plant Physiology, College of Agriculture 2024 - 215p.
Ph. D
217
KERALA AGRICULTURAL UNIVERSITY
COLLEGE OF AGRICULTURE, VELLAYANI
DEPARTMENT OF PLANT PHYSIOLOGY
DOCTORAL DEFENSE SEMINAR
ABSTRACT
Amrutha Vijayakumar Date: 07-10-2023
2020-21-014 Time: 11-11:30 am
RESPONSE MECHANISMS INDUCED BY EXPOSURE TO HIGH
TEMPERATURE IN TOMATO GENOTYPES AND DEVELOPMENT OF
SUITABLE MANAGEMENT STRATEGIES FOR ENHANCING THERMOTOLERANCE.
A study entitled “Response mechanisms induced by exposure to high
temperature in tomato genotypes and development of suitable management strategies
for enhancing thermo-tolerance” was conducted in the Department of Plant Physiology,
College of Agriculture, Vellayani during 2020-2023 with the objective of
physiological, biochemical and molecular characterization for high temperature
tolerance to identify key traits controlling high temperature tolerance in tomato and to
develop suitable management strategies to alleviate high temperature stress.
The first experiment involved the evaluation of 58 tomato genotypes (2 check
genotypes and 56 other genotypes) for temperature tolerance under field condition in
summer season. These fifty-eight genotypes were evaluated for physiological and yield
parameters under natural high temperature condition during summer season (February to
May, 2022). From this varietal screening experiment, the best performing genotypes in
terms of pollen viability, leaf membrane thermo-stability, chlorophyll fluorescence,
number of fruits, fruit set % were selected to determine the critical physiological and
biochemical characteristics regulating high-temperature tolerance in different tomato
genotypes for high-temperature tolerance under high-temperature circumstances.
During the Kharif months of 2022, from June to September, three tolerant and
three susceptible genotypes from the first varietal screening field experiment were
assessed both under high temperature (36 +/- 2°C) and ambient circumstances. The
experiment was set up using a completely randomized design (CRD), with three
replications of each of the two treatment levels-control and high-temperature stress.
Research demonstrated that factors, such as pollen viability (PV), cell membrane stability
(LMT), nitrate reductase (NR) activity, antioxidant enzymes, and their impact, has shed
information on the ability of plants to tolerate stress caused by high temperatures.
218
Genotypes like Vellayani Vijay, Kashi Vishesh and Anagha showed better performance
under heat stress conditions, by regulating some physiological parameters like higher PV,
LMT, PR, higher rates of production of antioxidant enzymes (superoxide dismutase,
sucrose phosphate synthase, invertase, nitrate reductase) and yield related observations
like fruit set percentage, average fruit weight were also high. These characteristics can be
considered as the key physiological, and biochemical traits controlling high temperature
tolerance in tomato. By creating a variety utilizing genetic techniques, genotypes with
higher thermotolerance, and thus negative effects of heat stress on tomatoes can be
reduced.
Under high temperature condition, Arka Vikas showed the highest exerted stigma
length and there is significant variation for flower burning and flower drop among all the
genotypes under study. With respect to yield, biochemical and physiological data the
changes in the tolerant and susceptible genotypes under HS conditions can be noted.
Tolerant genotypes (Kashi Vishesh, Vellayani Vijay) exhibited reduction in physiological
characteristics like LMT (5-7 %), PV (10-15%), total chlorophyll content (3-5%), PR (6-
17%), and an increase in SC (6-9%), CF (2-3%). In the similar way, biochemical
parameters in case of tolerant genotypes showed a reduction in SOD content (16-19%),
SPS (3-10 %), INV activity (3-7 %), NR activity (4-10%), total sugars (23-30%), and an
increase in anthocyanin (12-20%), flavanol (2-4%) were also recorded. Under heat stress
conditions only those genotypes that are tolerant produced higher fruit yield per plant
than the susceptible ones.
Similarly, reduction in features like LMT (10-22 %), PV (30-45 %), chlorophyll
content (11-14%), PR (20-32%), and increase in SC (11-22%) and CF (5-7%) has been
observed. Reduction in biochemical parameters under HS were SOD content (27-50%),
SPS (11-43 %), INV activity (11-13 %), NR activity (14-19%), total sugars (29-37%),
and an increase in anthocyanin (5-9%), flavanol (1-2%) were noticed in susceptible
genotypes like Arka Vikas, PKM-1 and Pusa Rohini under HS.
The reduction in fruit set % ranged from 30-50% in tolerant genotypes and was
ranging from 80-90% in susceptible ones. The yield attributes viz., number of fruits per
plant, fruit set %, average fruit weight (g), yield per plant (g) were significantly lower for
varieties like Arka Vikas, PKM-1 and Pusa Rohini. The reduction in number of fruits per
plant was nearly 30-40% in tolerant group whereas it was 80-98% in susceptible group.
The intensity of fruit drop increased at a range of 25-30% in tolerant genotypes whereas
it increased by 50-80% in susceptible genotypes. The reduction in yield per plant reduced
in both tolerant and susceptible genotypes and this ranged between 25-40% and 80-90%
respectively when plants were exposed to heat stress conditions.
219
An experiment was undertaken to develop suitable management strategies to
alleviate high temperature stress. One of the susceptible genotypes (Arka Vikas) and
two tolerant genotypes (Vellayani Vijay, Kashi Vishesh) were selected from previous
experiment and were evaluated for the study to develop the best suitable management
strategy to alleviate high temperature stress. The experiment was set up using CRD
with two factors, factor 1 being the two stress levels (control and high temperature
(36+/-2oC) and the second factor being the nine treatments- T1: Salicylic acid (1.0
mM), T2: Salicylic acid (1.5 mM), T3: Spermidine (2.5 mM), T4: Spermidine (4.0 mM),
T5: Brassinosteroids (0.3 mM), T6: Brassinosteroids (0.6 mM), T7: Piriformospora
indica, T8: Absolute control and T9: Control. The treatments, T1 to T6 were applied as
foliar spray at the flowering stage, T7 was inoculated to the roots by co-cultivation
method. The best management strategy to be recommended is spraying BR (0.3 mM)
and BR (0.6 mM) at the floral initiation stage to alleviate high-temperature stress. PR,
LMT, PV, fruit number, and average fruit set % were improved by these treatments,
antioxidant production and its activity, flavonol, anthocyanins and total sugars showed
significant increase in its content. Early flowering and fruiting were one of the
significant impacts of P. indica inoculation to roots in both tolerant and susceptible
genotypes.
The gene expression analysis of MYB33, HSFA1a, HSFB2a and alpha-amylase
transcription factors which are imparting high-temperature stress tolerance showed that
all the genes were upregulated under stress conditions for tolerant genotypes whereas
genes-alpha amylase, HSFA-1A, HSFB-2a were downregulated under stress conditions
and MYB33 gene were upregulated under stress.
Plant Physiology
Tomato genotypes
Thermo- tolerance
Tomato
571.2 / AMR/RE Ph. D
Response mechanisms induced by exposure to high temperature in tomato genotypes and development of suitable management strategies for enhancing thermo- tolerance - Vellayani Department of Plant Physiology, College of Agriculture 2024 - 215p.
Ph. D
217
KERALA AGRICULTURAL UNIVERSITY
COLLEGE OF AGRICULTURE, VELLAYANI
DEPARTMENT OF PLANT PHYSIOLOGY
DOCTORAL DEFENSE SEMINAR
ABSTRACT
Amrutha Vijayakumar Date: 07-10-2023
2020-21-014 Time: 11-11:30 am
RESPONSE MECHANISMS INDUCED BY EXPOSURE TO HIGH
TEMPERATURE IN TOMATO GENOTYPES AND DEVELOPMENT OF
SUITABLE MANAGEMENT STRATEGIES FOR ENHANCING THERMOTOLERANCE.
A study entitled “Response mechanisms induced by exposure to high
temperature in tomato genotypes and development of suitable management strategies
for enhancing thermo-tolerance” was conducted in the Department of Plant Physiology,
College of Agriculture, Vellayani during 2020-2023 with the objective of
physiological, biochemical and molecular characterization for high temperature
tolerance to identify key traits controlling high temperature tolerance in tomato and to
develop suitable management strategies to alleviate high temperature stress.
The first experiment involved the evaluation of 58 tomato genotypes (2 check
genotypes and 56 other genotypes) for temperature tolerance under field condition in
summer season. These fifty-eight genotypes were evaluated for physiological and yield
parameters under natural high temperature condition during summer season (February to
May, 2022). From this varietal screening experiment, the best performing genotypes in
terms of pollen viability, leaf membrane thermo-stability, chlorophyll fluorescence,
number of fruits, fruit set % were selected to determine the critical physiological and
biochemical characteristics regulating high-temperature tolerance in different tomato
genotypes for high-temperature tolerance under high-temperature circumstances.
During the Kharif months of 2022, from June to September, three tolerant and
three susceptible genotypes from the first varietal screening field experiment were
assessed both under high temperature (36 +/- 2°C) and ambient circumstances. The
experiment was set up using a completely randomized design (CRD), with three
replications of each of the two treatment levels-control and high-temperature stress.
Research demonstrated that factors, such as pollen viability (PV), cell membrane stability
(LMT), nitrate reductase (NR) activity, antioxidant enzymes, and their impact, has shed
information on the ability of plants to tolerate stress caused by high temperatures.
218
Genotypes like Vellayani Vijay, Kashi Vishesh and Anagha showed better performance
under heat stress conditions, by regulating some physiological parameters like higher PV,
LMT, PR, higher rates of production of antioxidant enzymes (superoxide dismutase,
sucrose phosphate synthase, invertase, nitrate reductase) and yield related observations
like fruit set percentage, average fruit weight were also high. These characteristics can be
considered as the key physiological, and biochemical traits controlling high temperature
tolerance in tomato. By creating a variety utilizing genetic techniques, genotypes with
higher thermotolerance, and thus negative effects of heat stress on tomatoes can be
reduced.
Under high temperature condition, Arka Vikas showed the highest exerted stigma
length and there is significant variation for flower burning and flower drop among all the
genotypes under study. With respect to yield, biochemical and physiological data the
changes in the tolerant and susceptible genotypes under HS conditions can be noted.
Tolerant genotypes (Kashi Vishesh, Vellayani Vijay) exhibited reduction in physiological
characteristics like LMT (5-7 %), PV (10-15%), total chlorophyll content (3-5%), PR (6-
17%), and an increase in SC (6-9%), CF (2-3%). In the similar way, biochemical
parameters in case of tolerant genotypes showed a reduction in SOD content (16-19%),
SPS (3-10 %), INV activity (3-7 %), NR activity (4-10%), total sugars (23-30%), and an
increase in anthocyanin (12-20%), flavanol (2-4%) were also recorded. Under heat stress
conditions only those genotypes that are tolerant produced higher fruit yield per plant
than the susceptible ones.
Similarly, reduction in features like LMT (10-22 %), PV (30-45 %), chlorophyll
content (11-14%), PR (20-32%), and increase in SC (11-22%) and CF (5-7%) has been
observed. Reduction in biochemical parameters under HS were SOD content (27-50%),
SPS (11-43 %), INV activity (11-13 %), NR activity (14-19%), total sugars (29-37%),
and an increase in anthocyanin (5-9%), flavanol (1-2%) were noticed in susceptible
genotypes like Arka Vikas, PKM-1 and Pusa Rohini under HS.
The reduction in fruit set % ranged from 30-50% in tolerant genotypes and was
ranging from 80-90% in susceptible ones. The yield attributes viz., number of fruits per
plant, fruit set %, average fruit weight (g), yield per plant (g) were significantly lower for
varieties like Arka Vikas, PKM-1 and Pusa Rohini. The reduction in number of fruits per
plant was nearly 30-40% in tolerant group whereas it was 80-98% in susceptible group.
The intensity of fruit drop increased at a range of 25-30% in tolerant genotypes whereas
it increased by 50-80% in susceptible genotypes. The reduction in yield per plant reduced
in both tolerant and susceptible genotypes and this ranged between 25-40% and 80-90%
respectively when plants were exposed to heat stress conditions.
219
An experiment was undertaken to develop suitable management strategies to
alleviate high temperature stress. One of the susceptible genotypes (Arka Vikas) and
two tolerant genotypes (Vellayani Vijay, Kashi Vishesh) were selected from previous
experiment and were evaluated for the study to develop the best suitable management
strategy to alleviate high temperature stress. The experiment was set up using CRD
with two factors, factor 1 being the two stress levels (control and high temperature
(36+/-2oC) and the second factor being the nine treatments- T1: Salicylic acid (1.0
mM), T2: Salicylic acid (1.5 mM), T3: Spermidine (2.5 mM), T4: Spermidine (4.0 mM),
T5: Brassinosteroids (0.3 mM), T6: Brassinosteroids (0.6 mM), T7: Piriformospora
indica, T8: Absolute control and T9: Control. The treatments, T1 to T6 were applied as
foliar spray at the flowering stage, T7 was inoculated to the roots by co-cultivation
method. The best management strategy to be recommended is spraying BR (0.3 mM)
and BR (0.6 mM) at the floral initiation stage to alleviate high-temperature stress. PR,
LMT, PV, fruit number, and average fruit set % were improved by these treatments,
antioxidant production and its activity, flavonol, anthocyanins and total sugars showed
significant increase in its content. Early flowering and fruiting were one of the
significant impacts of P. indica inoculation to roots in both tolerant and susceptible
genotypes.
The gene expression analysis of MYB33, HSFA1a, HSFB2a and alpha-amylase
transcription factors which are imparting high-temperature stress tolerance showed that
all the genes were upregulated under stress conditions for tolerant genotypes whereas
genes-alpha amylase, HSFA-1A, HSFB-2a were downregulated under stress conditions
and MYB33 gene were upregulated under stress.
Plant Physiology
Tomato genotypes
Thermo- tolerance
Tomato
571.2 / AMR/RE Ph. D