288 M. Saravanaraman et al.
Mutation Breeding for Sesame
Varietal Development
Crop improvement in sesame for such desirable
attributes is being attempted through convention-
al breeding methods, by exploiting the natural
variability available in the germplasm. However,
for changing the plant type, if adequate variabil-
ity is not available in the existing germplasm,
under such circumstances, mutation breeding can
be effectively employed as an alternative or sup-
plemental source (Anitha Vaseline et al. 2000 ).
In contrast to conventional breeding which may
require more time to develop a promising variety,
mutation breeding yields desirable crop variet-
ies in a shorter time. Considering the above, at-
tempts were made at Annamalai University, India
to develop high yielding, shoot webber resistant
sesame lines from already selected tolerant lines.
Mutagenesis
The parent materials chosen from earlier works
were subjected to mutation breeding using physi-
cal and chemical mutagens. For physical muta-
genesis, gamma rays were used. Freshly collected
sesame seeds were irradiated with 40, 50, and
60 krad, respectively. Irradiation was conducted
at Centre for Application of Radioisotopes and
Radiation Technology (CARRT), Mangalore Uni-
versity, Mangalore, India. Irradiated seeds were
sown in cement pots and maintained individually.
For chemical mutagenesis, two chemical
mutagens namely Ethyl Methane Sulfonate
(EMS) and Diethyl Sulfate (DES) were used.
To determine the LD 50 concentration for EMS,
freshly collected parent seeds were treated with
five concentrations of EMS namely 0.04, 0.05,
0.06, 0.07, and 0.08 %. The treated seeds were
placed on moist filter paper inside a petri plate
and observed for germination. Based on the ger-
mination percentage, LD 50 was ascertained. For
every treatment, five replications were main-
tained. Similarly, to ascertain the LD 50 for DES,
the solution was freshly prepared once in every
half an hour because of the shorter life period of
the chemical. Five concentrations namely 0.3,
0.4, 0.5, 0.6, and 0.7 % were evaluated. Based on
the LD 50 values for each chemical, the test dos-
ages were fixed. The treated seeds were washed
thoroughly several times with distilled water and
sown in cement pots under screenhouse condi-
tions and maintained as individual plants in each
pot. Untreated seeds were used as control. The
plants thus raised were evaluated for resistance
against A. catalaunalis.Mass Culturing A. catalaunalis
Sesame plants raised in earthen pots (30 cm diam-
eter and 30 cm high) were used for mass culturing
of A. catalaunalis. Seeds of sesame were sown
in the potting mixture comprising soil, farmyard
manure, and sand in the ratio of 2:1:1 which was
further amended with urea @ 2–3 g/pot. Sesame
plants were raised at regular interval so as to
maintain a continuous stock of young plants.
Mass culturing of A. catalaunalis was done
by collecting larvae from infested sesame fields.
The larvae were released on potted plants. The
potted plants were placed inside a cage consist-
ing of nylon net cloth affixed to an iron frame
(2.5 × 1.5 × 1.5 m). The cage was permanently
placed in a sunny area and 20 plants were en-
closed per cage. Fresh plants were provided as
and when needed for larval infestation. Thus the
larvae were allowed to grow without any distur-
bance until pupation. The pupae along with silk-
en cocoons were collected in small plastic cups
having a layer of cotton and kept inside a spe-
cially designed adult emergence and oviposition
cage. The cage consisted of a cylindrical glass jar
(15 cm high and 10 cm diameter) above which
mylar film sheet rolled cylindrically (30 cm high
and 10 cm diameter) was affixed. Fifteen days
old sesame seedlings were raised in the nursery
bag (12 × 8 cm) and kept inside the cage. Strips
of cloth (15 × 5 cm) were hung from the top of the
cage, so as to enable emerging moths for stretch-
ing their wings and cuticle hardening. The adults
were fed with 10 % sucrose solution through
soaked cotton wigs placed inside. Adults were