PhD

The study entitled ‘Heterosis breeding in sesame (Sesamum indicum L.)’ was
undertaken at the Department of Plant Breeding and Genetics, College of
Horticulture, Vellanikkara. The objectives of the study were to collect and evaluate
different genotypes of sesame for morphological traits and yield attributes, to identify
useful parents producing heterotic crosses and developing hybrids in sesame. The
study also intended to develop male sterile lines in sesame through interspecific
hybridization with Sesamum malabaricum.
Sesamum indicum and Sesamum malabaricum accessions were collected from
Kerala and Tamil Nadu and evaluated for their morphological traits. Wide range of
variation was noticed for characters like plant height, number of days to flowering and
seed yield per plant which contributed maximum to genetic divergence. The
genotypes studied were grouped into six clusters.
High genotypic coefficient of variation (GCV) was recorded for number of
capsules per plant, plant height, seed yield per plant and number of branches per
plant. High heritability with high genetic advance as per cent of mean was recorded
for number of days to flowering, plant height, number of branches per plant, number
of capsules per plant and seed yield per plant. This indicates that the characters are
governed by additive gene effects and selection for these traits will be effective.
Association analysis revealed that seed yield per plant was correlated to plant
height, number of capsules per plant and number of days to flowering. Path
coefficient analysis indicated maximum positive direct effect by number of capsules
per plant, capsule length, plant height and 1000 seed weight on seed yield per plant.
In order to develop hybrids, fourteen parents were selected based on the per se
performance of the genotypes. They were crossed in line X tester mating design.
Forty eight hybrid combinations obtained were raised in the field along with the
parents and evaluated for their heterosis and combining ability effects.
Parental genotypes AVTS-06-5, AVTS-06-10, IVTS-06-12, KYM-1, Tilak
and TMV-6 were identified as high combiners based on general combining ability
(gca) effects. Two combinations viz. AVTS-06-5 X KYM-1 and IVTS-06-12 X
TMV-3 had significant values of per se performance, specific combining ability (sca)
effects and standard heterosis for seed yield per plant. They can be evaluated for their
hybrid vigour over locations and seasons.
The crosses AVTS-06-5 X TMV-3, AVTS-06-5 X TMV-6 and TCR 3279A X
KYM-1 have been identified as potential cross combinations for isolation of
promising segregants as the parents involved in these crosses had high significant gca
effects for seed yield per plant but the hybrids recorded non significant sca effects.
Interspecific hybridization between S.malabaricum and S.indicum was
attempted to develop male sterile lines. Seed set was noticed in three interspecific
hybrids which failed to germinate due to embryo abortion. Hence these embryos were
rescued and raised in vitro to obtain the hybrids.