ANTIBIOSIS TO BEET ARMYWORM (SPODOPTERA-EXIGUA) IN LYCOPERSICON ACCESSIONS

Four accessions of Lycopersicon hirsutum f. glabratum Mull. and eight accessions of L. hirsutum f. typicum Humb. & Bonpl. were evaluated for their resistance to the beet armyworm [Spodoptera exigua (Hubner)]. S urvival of S. exigua neonate larvae for up to 96 hours on foliage of a ll these accessions differed significantly from their survival on a su sceptible tomato cultivar. Spodoptera exigua survival did not differ s ignificantly between the two forms of L. hirsutum. Antibiosis to S. ex igua in L. hirsutum f. glabratum appears similar to the levels found t o other Lepidoptera. Accessions of L. hirsutum f. typicum included the very susceptible PI 199381 and the two most resistant accessions, LA 2329 and LA 1777. Insect resistance had not been reported previously i n four of the L. hirsutum f. typicum accessions. Spodoptera exigua sur vival was significantly negatively correlated with the density of type IV glandular trichomes on the leaf surfaces, calculated across all 12 accessions. This relationship did not occur within L. hirsutum f. gla bratum or L. hirsutum f. typicum accessions, nor was it significant if PI 199381 was excluded from the analysis. Leaf-surface exudates of L. hirsutum f. glabratum accessions were dominated by the methylketones 2-undecanone and 2-tridecanone. Leaf-surface exudates of L. hirsutum f . typicum were dominated by three sesquiterpenes-zingiberene, delta-el emene, and gamma-elemene. Resistance was not correlated with the amoun ts of these specific compounds within or across botanical form. Spodop tera exigua survival in L. hirsutum f. typicum (excluding PI 199381) c orrelated negatively with the total estimated amount of leaf-surface v olatiles extracted. PI 199381 may be useful as a susceptible parent fo r intraspecific crosses to examine S. exigua resistance in L. hirsutum .