GENETIC-BASIS OF RESISTANCE AGAINST 2 TOSPOVIRUS SPECIES IN TOMATO (LYCOPERSICON-ESCULENTUM)

Inheritance studies were conducted to determine the genetic basis of resistance in tomato (Lycopersicon esculentum) against two distinct Tospovirus species (tomato spotted wilt virus and tomato chlorotic spot virus) belonging to the 'tomato spotted wilt virus complex' identified in Brazil. F-1,F- backcrosses and F-2 populations were developed using the resistant parent 'CNPH Tx 405' and susceptible parent 'IPA5'. Segregation ratios indicated that the inheritance of resistance to both viruses fit a single dominant gene-model. Preliminary tests using data from 50 pairs of vegetatively propagated F-2 plants (inoculated separately with each virus) indicated that the same gene (probably the Sw-5 gene) is controlling the resistance to both viruses. This gene displays a peculiar mode of action, closely resembling a vertical resistance response, but acting against a large number of phenotypic variants and species within the genus Tospovirus.