Evaluation of tomato (Lycopersicon esculentum Mill.) plants with natural and transgenic resistance against Tomato spotted wilt virus (TSWV) isolates occurring in the Republic of South Africa (RSA)

Abstract

Tomato spotted wilt virus (TSWV) infections causes significant economic losses in the commercial production of tomato (Lycopersicon esculentum Mill.). This study was undertaken to evaluate tomato with natural and transgenic resistance when inoculated with TSWV isolates occurring in the Republic of South Africa (RSA). The Stevens cultivar which has natural resistance to TSWV conferred by the Sw-5 gene and the transgenic 13-1 line which expresses the nucleocapsid (N) protein gene of the TSWV-BL isolate were used as test plants. Six TSWV isolates collected from Gauteng, KwaZulu-Natal, North West, Limpopo and Mpumulanga provinces were mechanically inoculated onto test plants. The trial was arranged in a general treatment structure with randomized block design and repeated once. Plants were assessed for TSWV resistance based on a disease severity rating scale and measurements of virion accumulation levels (A405nm) using Enzyme linked immunosorbent assay (ELISA)[A1]. There were no significant differences among the reactions produced by the six TSWV isolates on the test plants. Although both plants were susceptible to the TSWV isolates from RSA by exhibiting similar high viral accumulation levels, the transgenic tomato line showed milder disease severity than the natural resistant cultivar. Results suggest that transgenic resistance is a more viable approach in the control of TSWV in RSA. Key words: Tomato spotted wilt virus (TSWV), Republic of South Africa, virus resistance, transgenic, tomato (Lycopersicon esculentum Mill.).