Evaluation of Lycopersicon Germ Plasm for Tomato Spotted Wilt Tospovirus Resistance by Mechanical and Thrips Transmission. N. K. Krishna Kumar, Department of Entomology, University of Hawaii, 3050 Maile Way, Honolulu 96822. Diane E. Ullman, and John J. Cho. Department of Entomology, University of Hawaii, 3050 Maile Way, Honolulu 96822; and Department of Plant Pathology, University of Hawaii, Maui Research Station, P.O. Box 269, Kula 96790. Plant Dis. 77:938-941. Accepted for publication 5 May 1993. Copyright 1993 The American Phytopathological Society. DOI: 10.1094/PD-77-0938.

Selected tomato germ plasm representing eight Lycopersicon species and five cultivars of L. esculentum was evaluated for resistance to a Hawaiian isolate of tomato spotted wilt tospovirus (formerly designated TSWV-L). A comparison of mechanical and thrips inoculation of TSWV across these accessions demonstrated that the two inoculation methods provide different evaluations of tomato germ plasm. Mechanical inoculation was useful in identifying direct TSWV resistance, such as virus replication and translocation. In contrast, thrips inoculation was most useful in identifying insect-mediated components of TSWV resistance, such as those associated with changes in feeding behavior. Although both inoculation methods resulted in systemic TSWV infection in all accessions except Lycopersicon peruvianum, the percentage of infection varied significantly among germ plasm screened within and between inoculation methods. While L. parviflorum, a wild species, was the most susceptible accession, L. pennellii, L. chilense, and L. peruvianum were least susceptible to TSWV with both mechanical and thrips inoculations. Thrips inoculation resulted in significantly fewer infected plants compared to mechanical inoculation on L. esculentum cultivars Manzana, Brazil, and Anahu, and on L. hirsutum f. glabratum, indicating resistance to thrips transmission of TSWV. The differences observed between mechanical and thrips inoculation suggest that one should consider results obtained by both methods when evaluating accessions for resistance to TSWV.

Keyword(s): Frankliniella occidentalis, western flower thrips.