PhD

An experiment on "Gene action and heterosis for yield, quality and
fruit borer sresistance in tomato (Lycopersicon esculentum Mill.)" was
carried o~t at the Department of Plant Breeding and Genetics, College of
Agriculture, Vellayani during 1999-2002 with the objective of estimating
the combining ability, heterosis and gene action involved in the
inheritance of yield, quality and fruit borer resistance.
Forty diverse genotypes were collected from Asian Vegetable
Research and Development Centre (A VRDC), Taiwan and all over India.
These were evaluated in the field for yield and quality characters and
insect resistance in a net house, each being replicated twice. Analysis of
variance revealed significant genotypic difference for all the characters
studied.
The observations recorded were plant height, number of branches,
spread of the plant, number of days to first flowering, number of days to
first fruit harvest, number of fruits per plant, weight of fruits per plant,
weight of individual fruit, number of locules per fruit, number of seeds per
fruit, pericarp thickness, vitamin C, carotene, pH of juice, TSS, sugar
content, shelf life and percentage of'fruit borer infested fruits per plant.
Variabili ty studies indicated high GCV and PCV for the characters number
of fruits per plant, weight of fruits per plant and carotene .
. High estimates of heritability (>70 %) were recorded for most of the
characters studied. High heritability (>70 %) combined with high genetic
advance (>70 %) was observed for number of fruits per plant, weight of
fruits per plant and carotene content of fruits. Fruit yield per plant
showed significant positive correlation with plant height, number of
branches per plant, spread of plant, number of fruits per plant and weight
of individual fruit.

A discriminant function was fitted with seventeen variables to derive
a performance index for the forty genotypes. The top five scorers, EC-461 070,
EC-461018, EC-461078, Arka Alok and PKM 1 along with a popular
variety Mukthi were selected as lines (female parents) for hybridization
and three testers (male parents) MTM Local, EC-461035 and EC-461057
with very low fruit borer infestation were selected for hybridization.
Combining ability analysis showed that the lines EC-461070,
EC-461 0 18 and tester MTM Local were good general combiners with
respect to fruit yield and quality attributes whereas EC-461 070, Arka Alok
and PKM 1 and MTM Local were good general combiners for fruit borer
resistance. Among the eighteen hybrid combinations, signi ficant sea
effects was observed in the hybrids, EC-461070 x MTM Local,
EC-461018 x EC-461035 and PKM I x EC-461057. Among the hybrids
EC-461070 x MTM Local showed significant sca effect for fruit yield,
number of fruits, individual fruit weight, plant height, number of branches,
spread of plant, number of seeds per fruit and pericarp thickness.
Significant positive relative heterosis for fruit yield was recorded by
five hybrids. Among this, two hybrids, vi i ., EC-461 070 x MTM Local and
PKM 1 x EC-461057 also recorded significant positive heterobeltiosis.
The best cornbiner EC-461 070 x MTM Local recorded significant positive
standard heterosis for plant height, number of branches, spread of the
'plant, number of fruits per plant, weight of fruits per plant, weight of
individual fruit, number of locules per fruit, number of seeds per fruit,
carotene content, TSS and significant negative heterosis for pericarp
thickness, pH of juice and shelf life.
Generation mean analysis was carried out using six parameter model.
Six generations, viz., PI, P2, FI, F2, Bland B2 were built up using the cross
EC-461070 x MTM Local. It was found that the gene actions namely
additive, dominance and epistatic interactions were present for all the
characters studied.