Interaction between ‘Candidatus Phytoplasma australasiae’ and Tomato yellow leaf curl virus in tomato plants

Abstract

To evaluate the effect of mixed infection of two main pathogens of tomato in Iran, the interaction between tomato big bud phytoplasma (TBBP, 16SrII-D) and Tomato yellow leaf curl virus (TYLCV) was investigated under greenhouse condition. Tomato plants were graft-inoculated either with TBBP or TYLCV alone or together simultaneously and non-simultaneously. Symptoms expression and incubation period of the diseases were evaluated on all inoculated plants. To assess pathogen development, the concentrations of TBBP and TYLCV were compared at 10, 20, 40 and 70 days post-inoculation using quantitative PCR assays. In all replications, the tomato plants doubly inoculated with TBBP + TYLCV showed milder symptoms and longer incubation period than those singly inoculated with TBBP or TYLCV. Results also showed a reduction of TYLCV and TBBP concentrations in doubly inoculated plants when compared to single infection, although these reductions were not always statistically significant. In the tomato plants simultaneously inoculated with TBBP and TYLCV, the phytoplasma and virus concentrations were significantly lower at 70 days post-inoculation. These results suggest an antagonism between TYLCV and TBBP when infecting the tomato plant.