Ph D

The present investigation entitled ‘‘Gene action and gene expression analysis in
tomato (Solanum lycopersicum L.) under moisture stress” was conducted during the
period 2017-2021, in the Department of Plant Breeding and Genetics, College of
Agriculture, Vellayani.
Thirty-two genotypes including local genotypes of tomato were collected from
different sources and studied under three different experiments.
In the first experiment, twenty-one F1 hybrids derived from the line x tester mating
and their ten parents were transplanted in the field and the treatment mean sum of square
due to genotypes was found to be highly significant for all the characters studied which
would ultimately indicate diverse nature of selected genotypes. The mean performance
showed wide range of variation for most of the characters studied. Among lines, L7 (Pusa
Ruby) showed higher mean performance for all-out of nine characters viz., plant height,
fruit length, fruit girth, fruit volume, fruit weight, yield per plant, yield per plot, root
length, root volume and relative water content.
Among three testers, T2 (Kuttichal Local) showed favourable mean performance
for seventeen traits viz., plant height, primary branches per plant, number of leaves per
plant, number of flowering clusters per plant, number of fruits per cluster, fruit length,
fruit girth, fruit volume, fruit weight, yield per plant, yield per plot, vitamin C, total
acidity, stomatal frequency, root length, root volume and proline content.
Under moisture stress (Second experiment), among the lines, L7 (Pusa Ruby)
showed higher mean performance for eleven characters viz., plant height, fruit length,
fruit girth, fruit volume, fruit weight, yield per plant, yield per plot, total soluble solids,
root length, root volume and pollen viability.
Among three testers, T2 (Kuttichal Local) showed favourable mean performance
for sixteen traits viz., plant height, primary branches per plant, number of leaves per plant,
number of flowering clusters per plant, number of fruits per cluster, number of fruits per
plant, fruit length, fruit girth, fruit volume, total soluble solids, total acidity, stomatal
frequency, root length, root volume and canopy temperature.
Based on general combining ability analysis, the line L6 (Arka Alok) ranked as
top by exhibiting significant gca effects for six traits viz., fruit length, fruit girth, fruit
volume, fruit weight, specific leaf area and root length. Among the testers, T3 (Kottayam
Local) had superior gca effects for Days to 50% flowering, number of flowering clusters
per plant, number of fruits per cluster, fruit length, fruit volume, yield per plot, total
soluble solids, lycopene, titrable acidity canopy temperature and proline content.
Under moisture stress, the line L3 (Akshaya) ranked as top by exhibiting
significant gca effects for ten traits viz., primary branches per plant, number of fruits per
cluster, number of fruits per plant, fruit weight, yield per plant, yield per plot, stomatal
frequency, specific leaf area, canopy temperature and pollen viability. Among the testers,
T1 (Palakkad Local) had superior gca effects for plant height, number of fruits per cluster,
number of fruits per plant, fruit girth, fruit volume, yield per plant, yield per plot, total
soluble solids, relative water content, canopy temperature and proline content.
In the case of hybrids, Based on mean performance, the crosses L1 x T1 (Vellayani
Vijay x Palakkad Local), L2 x T3 (Anagha x Kottayam Local), L3 x T1 (Akshaya x
Palakkad Local), L3 x T3 (Akshaya x Kottayam Local), L4 x T1 (PKM 1 x Palakkad Local),
L4 x T2 (PKM 1 x Kuttichal Local), L5 x T1 (Arka Meghali x Palakkad Local), L5 x T2
(Arka Meghali x Kuttichal Local), L5 x T3 (Arka Meghali x Kottayam Local), L6 x T2
(Arka Alok x Kuttichal Local) and L6 x T3 (Arka Alok x Kottayam Local) were superior
for different yield characters.
Under moisture stress, Hybrids L3 x T1 (Akshaya x Palakkad Local), L3 x T3
(Akshaya x Kottayam Local), L4 x T1 (PKM 1 x Palakkad Local), L4 x T2 (PKM 1 x
Kuttichal Local), L5 x T2 (Arka Meghali x Kuttichal Local), L7 x T2 (Pusa Ruby x
Kuttichal Local) and L7 x T3 (Pusa Ruby x Kottayam Local) were superior for yield based
on mean value.
Based on combining ability studies under normal field condition, identified
superior crosses such as L1 x T1 (Vellayani Vijay x Palakkad Local), L2 x T1 (Anagha x
Palakkad Local), L2 x T3 (Anagha x Kottayam Local), L3 x T1 (Akshaya x Palakkad
Local), L3 x T3 (Akshaya x Kottayam Local), L4 x T1 (PKM 1 x Palakkad Local), L4 x T2
(PKM 1 x Kuttichal Local), L6 x T2 (Arka Alok x Kuttichal Local), L6 x T3 (Arka Alok x
Kottayam Local), L7 x T1 (Pusa Ruby x Palakkad Local) and L7 x T3 (Pusa Ruby x
Kottayam Local) exhibited higher sca effects for yield per plant.
Under moisture stress, identified superior crosses such as L1 x T2 (Vellayani Vijay
x Kuttichal Local), L2 x T3 (Anagha x Kottayam Local), L3 x T1 (Akshaya x Palakkad
Local), L4 x T2 (PKM 1 x Kuttichal Local), L5 x T2 (Arka Meghali x Kuttichal Local), L6
x T2 (Arka Alok x Kuttichal Local) and L7 x T3 (Pusa Ruby x Kottayam Local) exhibited
higher sca effects for yield per plant.
Based on heterosis, Overall, nineteen hybrids (L1 x T1, L1 x T2, L1 x T3, L2 x T1, L2
x T2, L2 x T3, L3 x T1, L3 x T3, L4 x T1, L4 x T2, L4 x T3, L5 x T1, L5 x T2, L5 x T3, L6 x T1, L6
x T2, L6 x T3, L7 x T1 and L7 x T3) from twenty one crosses revealed significant and positive
heterobeltiosis for yield per plant under normal field condition.
In the case of gene action, dominance genetic variance (σ2D) is higher than
additive genetic variance (σ2A) was observed for all the traits under normal field condition
and water stress condition, indicating that traits are controlled by non-additive gene
action.
Correlation study revealed yield per plant was positively and significantly
correlated with the traits viz., primary branches per plant, number of flowering clusters
per plant, number of fruits per cluster, number of fruits per plant, fruit girth, fruit volume,
fruit weight and yield per plot.
Based on qRT-PCR, the expression of both genes (moisture stress related genesSlDREB 1 and SlWRKY 4) was upregulated under water stress in all selected genotypes
and the expression was more than moisture stress tolerant check variety. The result is in
accordance with the analysis of moisture stress related physiological characters in these
genotypes in the field under stress.
From the study, identified tolerant sources for moisture stress viz., Akshaya, Pusa
Ruby and Kuttichal Local, these lines and tester can be used in breeding programmes for
moisture stress tolerance. Based on mean performance and gca, the genotypes Vellayani
Vijay, Akshaya, Arka Meghali, Arka Alok and Kottayam local which showed superiority
in yield and fruit quality traits can be used for breeding for improvement of yield and
quality traits. The hybrids L3xT1 (Akshaya x Palakkad Local), L4 x T2 (PKM 1 x Kuttichal
Local), L5 x T2 (Arka Meghali x Kuttichal Local) and L7 x T3 (Pusa Ruby x Kottayam
Local) which showed superiority for yield and quality characters with tolerance to
moisture stress can be recommended for release after yield trials.