Temporal Dynamics of Tomato Severe Rugose Virus and Bemisia tabaci in Tomato Fields in Sao Paulo, Brazil

摘要

Temporal progress of a begomovirus disease in tomato fields and the abundance of its whitefly vector, Bemisia tabaci biotype B, were evaluated during three consecutive tomato plantings in the municipality of Sumare, state of Sao Paulo, Brazil, in 2006 and 2007. The incidence of symptomatic plants and the number of adult whiteflies were weekly monitored on experimental plots randomly chosen in tomato commercial fields. Tomato severe rugose virus (ToSRV) was identified as the causal agent of the disease, and its relationships with other Brazilian begomoviruses was confirmed by partial and complete nucleotide sequencing of the viral genome. The disease temporal progress was analysed by fitting different models to disease incidence. The monomolecular model showed the best fit, which is consistent with a predominant role of primary spread in the epidemiology of ToSRV. A higher number of adult whiteflies were observed at the borders of the plots, also suggesting primary spread of ToSRV from external sources of inoculum, which might be represented by weeds and volunteer tomato-infected plants. In Brazil, since 2004, there is a legislative measure that mandates, for some regions of processing tomato plantings, a 2-month crop-free period during the year. Based on our results, we suggest the extension of this measure to all tomato-producing regions, including fresh market tomato. We also suggest that growers emphasize the elimination of old plants from harvested fields that can serve as virus reservoirs several weeks prior to new plantings and weeds nearby the fields to limit the primary spread of ToSRV.