A rapid and efficient inoculation method for Tomato spotted wilt tospovirus

A rapid and efficient method of inoculation for Tomato spotted wilt tospovirus (TSWV) was achieved by applying the inoculum with a device consisting of a spray gun, an atomizer and a CO2-powered sprayer. The inoculum contained infected leaf sap prepared in 0.1 M phosphate buffer, pH 7.0, 0.2% sodium sulfite and 0.01 M 2-mercaptoethanol (1 g: 10 ml) and 1% each of Celite 545 and Carborundum 320 grit. The spray application of chilled inoculum at the rate of 1.1 ml/plant and at an air pressure of 4.1 bar resulted in systemic infection nearly to a 100% of the tobacco (Nicotiana tabacum) plants inoculated. The inoculation procedure was successfully applied to two other important host species of TSWV, peanut (Arachis hypogaea) and tomato (Lycopersicon esculentum), where 75.0–100% and 72.2–91.6% plants developed systemic infection, respectively. The approach facilitated a much faster inoculation of test plants with TSWV as it was estimated to be about 50 times quicker (depending on the plant species) than the hand inoculation. The procedure is suitable for rapid and simultaneous inoculation of a large number of test plants with TSWV and should facilitate screening of germplasm and breeding lines for virus resistance.