Correlation between whitefly (Homoptera : Aleyrodidae) feeding behavior and transmission of tomato yellow leaf curl virus

The feeding behavior of the whitefly Bemisia tabaci (Gennadius) was monitor ed using the electrical penetration graph (EPG) technique during the transm ission process of tomato yellow leaf curl geminivirus (TYLCV). The behavior of individual viruliferous whiteflies was recorded on two-leaf stage tomat o test plants (Lycopersicon esculentum Mill 'Riofuego'). A total of 213 whi tefly individuals was recorded on single test plants during an inoculation access period that ranged from 3.5 to 14 h. Recordings were classified into 4 categories depending of the waveforms observed: group I, including only waveform C (pathway), was associated with a residual 2.4% TYLCV transmissio n efficiency; group II, showing stylet pathway and a single E(pd)(1) wavefo rm, was associated with a 7.4% transmission efficiency; group III, showing stylet pathway and a single E(pd)(1) + E(pd)(2) waveform, achieved a 23.4% transmission efficiency; and finally group TV, showing pathway followed by several E(pd)(1) + E(pd)(2) waveforms, was associated with the highest tran smission efficiency (37.5%). A total of 16 different behavioral variables w as introduced into a stepwise-backward logistic regression model to determi ne the variables most related to TYLCV inoculation. Among them, the total d uration of E(pd)(1) was the most significant variable associated with virus inoculation by B. tabaci (P = 0.002, positive relationship). In addition, the regression analysis indicated a strong positive relationship (P = 0.005 ) between transmission efficiency and total number of E (pd)(1) (t = 4.39, beta = 0.45 +/- 0.10, r = 0.87), and total duration of waveform E(pd)(1) (P = 0.05) (t = 4.00, beta = 0.02 +/- 0.001, r = 0.94). The minimum phloem co ntact E(pd)(1) threshold period observed for successful inoculation of TYLC V by B. tabaci on tomato plants was 1.8 min. Implications of these results for. persistent virus transmission by whiteflies are discussed.