Resistance to Tomato chlorosis virus in wild tomato species that impair virus accumulation and disease symptom expression.

Tomato chlorosis virus (ToCV) (genus Crinivirus, family Closteroviridae) is an emerging threat to tomato crops worldwide. Although symptoms on fruits are not obvious, yield losses occur through decreased fruit size and number. Control of ToCV epidemics is difficult because the virus is transmitted by several whitefly vector species and its relatively wide host range facilitates establishment in local wild reservoirs. Therefore, breeding for ToCV resistance offers the best control alternative. However, no sources for resistance are available thus far. Here, a screen of tomatoes and wild species relatives was performed in search of ToCV resistance. Two sources of resistance to ToCV were identified in this work, lines '802-11-1' and '821-13-1', each derived by two self-pollinations from ToCV asymptomatic plants of the population 'IAC CN RT' (derived from an interspecific hybrid Solanum lycopersicum x S. peruvianum accession LA0444) and accession LA1028 (S. chmielewskii), respectively. The resistance was expressed by impairing virus accumulation and disease symptom expression, both under natural infection and after challenging with ToCV in controlled inoculations. Genetic control of resistance to ToCV infection in '821-13-1' was conferred by a major locus with mainly additive effects but also partial dominance for higher susceptibility. Also, an additive x dominance epistatic interaction with at least one additional gene was evident.