Redesigning Research on Crop Resistance to Insects: Experiences with Tomato 301
germination. Based on these values, seeds, pre-
soaked in distilled water for 6 h were treated
with DES @ 0.09, 0.1, and 0.2 % and EMS @
0.2, 0.3, and 0.4 % for 12 h. After the treatment,
seeds were washed in sodium thiosulfate buffer
and distilled water.
For physical mutation, the seeds of the selected
tomato accessions were treated with gamma rays
at the radiation frequency of 5, 10, and 15 kR in
the Gamma Chamber 1200, supplied by Board of
Radiation and Isotope Technology (BRIT), De-
partment of Atomic Energy (DAE), Government
of India, Mumbai, India and established at the
Centre for Plant Breeding and Genetics, Tamil
Nadu Agricultural University, Coimbatore, India.
The mutagenized seeds were sown in earthen
pots and 25 days old seedlings were transplant-
ed in the field for resistance evaluation against
H. armigera and B. tabaci. Three field trials were
conducted respectively for the M1, M2, and M3
generations of mutagenized tomato accessions.
Population of H. armigera larvae and B. tabaci
nymphs was recorded and the mutant generations
were rated for resistance.
In the field trials, larval population of
H.armigera was found the least in mutagenized
tomato accession Varushanadu Local in all the
three generations (Table 12 ). In the M1 genera-
tion, plants of this accession mutagenized with
DES @ 0.1 % recorded the least population. But
in the M2 and M3 generation, plants mutagenized
with EMS @ 0.4 % recorded the least population.
With regard to whitefly population, wider varia-
tion was observed among mutagens and theirTable 11 Evaluation of backcross progenies of promising tomato accession against key insect pests
Accession/Hybrid Mean larval/nymphal population per plant Percent leaf infestation L.
H. armigera S. litura B. tabaci trifolii
PKM1 0.32 0.36 1.07 21.42
Varushanadu Local (VL) 0.06 0.06 0.05 8.12
PKM1 × VL (F 1 ) 0.26 0.30 0.45 20.48
VL × PKM1 (F 1 ) 0.08 0.18 0.21 18.24
(PKM1 × VL) × PKM1 (BC 1 ) 0.06 0.08 0.08 9.86
(VL × PKM1) × PKM1 (BC 1 ) 0.08 0.08 0.11 17.22
(VL X PKM1) × VL (BC 1 ) 0.16 0.26 0.26 18.96
(PKM1 X VL) × VL (BC 1 ) 0.18 0.24 0.23 18.52
C.D. ( p = 0.05) 0.01 0.02 0.05 1.56
Each value is a mean of five replications
Table 12 Field evaluation of tomato mutants against H. armigera
Mutagen Larval population per plant
M1 M2 M3
Conc./Dose VL I 979 VL I 979 VL I 979
DES
0.09 % 1.98 4.66 1.49 4.66 3.49 5.89
0.1 % 0.89 3.55 1.94 4.83 3.16 4.98
0.2 % 1.94 3.16 2.39 4.61 2.44 4.22
EMS
0.2 % 2.21 3.83 2.05 5.16 3.32 5.61
0.3 % 2.49 5.28 1.44 3.67 3.30 5.05
0.4 % 2.55 4.17 0.94 3.94 1.22 3.44
Gamma rays
5 KR 2.43 4.38 2.44 3.50 1.98 4.77
10 KR 2.11 4.56 2.16 4.94 3.50 6.22
15 KR 2.38 5.22 3.27 4.60 3.99 5.83
Control 4.43 6.88 4.39 6.67 5.55 7.61
C.D. ( p = 0.05) 0.56 0.75 0.37