The purpose of the present work was the characterization of the temporal and spatial pattern of Tomato yellow vein streak virus (ToYVSV), transmitted by the whitefly Bemisia tabaci, in tomato crops under field and greenhouse conditions, in Sumaré and Elias Fausto counties, respectively, State of São Paulo, Brazil. A total of 4,032 plants of cultivar Alambra, distributed in eight randomized blocks, were evaluated under field conditions. Evaluations in greenhouses were performed on 6,016 plants of cultivar Ikram. Plants were transplanted into eight greenhouses, in a staggered manner. Evaluations were based on typical symptoms induced by this begomovirus. The identification of the virus species was based on the analysis of the nucleotide sequence of part of the DNA-A (810 bp), which included the AV1 and AC3 genes. The incidence of the disease progressed very slowly under field conditions, coming from a minimum of 0.002 (proportion of symptomatic plants) to a maximum of 0.0497. In spite of this, border effect was observed, since the average of diseased plants in the peripheric blocks was 2.1 times higher than in the inner blocks. The disease progress curve was linear, indicating that newer infections were mainly due to the constant influx of viruliferous whiteflies coming from outside sources of inoculum. The percentage of diseased plants in tomatoes grown under greenhouse conditions was enormously influenced by the time of planting, varying from 4.8% to 69.3%. The spatial distribution of symptomatic tomato plants in these crops was aggregated. Apparently, this pattern was not due to secondary infections, but a result of aggregation of diseased plants near the periphery of the greenhouses. Based on these results, it is suggested that the elimination of sources of inoculum represented by old tomato crops and infected weed hosts is one of the most important practices for disease management.
Lycopersicon esculentum; Aleyrodidae; binomial dispersion index; Taylor law; begomovirus
