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Antixenosis resistance to Helicoverpa armigera (Lepidoptera: Noctuidae) was studied in 10 tomato accessions selected from a germplasm of 321 at Tamil Nadu, India, using free-choice and no-choice laboratory experiments. The foliage and fruits of two accessions, namely PT 4287 and Varushanadu Local were the least preferred for feeding in both tests. In the no-choice (confinement) test, Seijima Jeisei, Varushanadu Local and PT 4287 were the most preferred for oviposition, but had low egg hatch rates. In the freechoice test, these accessions were the least preferred for oviposition. The first and second instars preferred to feed on the foliage of 30-and 45-day-old plants, respectively than 60-and 75-day-old plants, whereas ovipositional preference was insignificant among the various plant ages.

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Four tomato accessions, namely Ac 238, Roma, Seijima Jeisei and Varushanadu Local selected from preliminary screening of 321 accessions and their hybrid derivatives, namely HY1F1 (Varushanadu Local × Ac 238), HY2F1 (Varushanadu Local × Roma), HY3F1 (Ac 238 × Roma) (first generation), HY1F2, HY2F2 and HY3F2 (second generation) were evaluated for their resistance in comparison with a susceptible check, 1979 against the leaf caterpillar, Spodoptera litura Fab. both under field and laboratory conditions at Annamalainagar, Tamil Nadu, India. In the field evaluation, accession Seijima Jeisei and hybrid HY3F1 recorded the minimum larval population. In glasshouse and laboratory studies, Seijima Jeisei was the least preferred by S. litura for both feeding and oviposition. The hybrid HY3F1 exerted pronounced antibiosis effect on S. litura. Among the various biophysical and biochemical bases of resistance, contents of reducing sugar and phenol were found negatively correlated with S. litura larval feeding. Among the hybrids, HY3F1 and HY3F2 and the parent Seijima Jeisei recorded higher fruit yield per plant in both seasons. Considerable variation in the resistance traits of the hybrids was observed when compared with the parents.