Relationships of the Sardinian isolate of tomato yellow leaf curl geminivirus with its whitefly vectorBemisia tabaci Gen

Relationships of an Italian isolate of tomato yellow leaf curl geminivirus from Sardinia (TYLCV-S) with its whitefly vectorBemisia tabaci were studied by means of experimental transmissions from tomato to tomato plants. TYLCV-S was confirmed to be transmitted in a persistent, circulative manner. The minimum latent period in the vector was between 17 and 20 h from the beginning of the acquisition access period (AAP). The maximum retention of infectivity was 8 days from the end of the AAP. Both acquisition and inoculation feeding times influenced the detected proportion of infective insects, with patterns well described by an exponential model. Acquisition was more efficient than inoculation. Males were significantly less efficient vectors than females. Nymphs were as efficient as adults in acquiring the virus. The length of AAP influenced both the retention of infectivity, and the pattern of transmission in serial transfer transmission tests with individual females. No significant difference in transmission efficiency was detected between two colonies ofB. tabaci, one inducing typical silverleaf symptoms on squash, the other inducing only mild symptoms with more than 50 whiteflies per plant. The phenomenon of periodic acquisition was not unequivocally proved for TYLCV-S.Research supported by the National Research Council of Italy, Special Project RAISA, Sub-project N. 2. Paper N. 1961.Supported by a grant from the Istituto Agronomico Mediterraneo, Valenzano (Bari), Italy.