Archivio Journal of Plant Pathology

Beet curly top Iran virus (BCTIV) is a member of ge- nus Becurtovirus, family Geminiviridae, which constrains host crop production in various geographical regions in Iran. This virus causes significant crop loss in sugar beet and has been also reported from other hosts including to- mato. Various plant factors such as resistance genes and microRNA pathways were found to be involved in plant– geminivirus interaction. Ty resistant hybrids were found to confer resistance to both monopartite and bipartite bego- moviruses through increasing cytosine methylation of the viral genome. In this study we investigated the response of various tomato cultivars and Ty resistant hybrids to BCTIV infection. In addition, the effect of the virus on the regula- tion of microRNA target genes in plant development was investigated. Based on the evaluated disease severity in- dex and coefficient of infection, Ty resistant hybrids were grouped as moderately susceptible plants and produced leaf curling symptoms after BCTIV infection. However, no clear symptom was observed in the cultivar Super Chief. In addition, a significantly lower level of virus accumula- tion was observed in Super Chief plants compared to the susceptible cultivar, Grosse Lisse. Expression analysis of miRNA target genes in infected plants showed that AGO1 was induced in both cultivars. However, MYB33 and AP2 were differentially regulated in the susceptible and mod- erately resistant cultivars. The importance of regulation of these miRNA target genes in viral symptom development is discussed.