RELATIONSHIPS OF THE SARDINIAN ISOLATE OF TOMATO YELLOW LEAF CURL GEMINIVIRUS WITH ITS WHITEFLY VECTOR BEMISIA-TABACI GEN

Relationships of an Italian isolate of tomato yellow leaf curl geminiv irus from Sardinia (TYLCV-S) with its whitefly vector Bemisia tabaci w ere studied by means of experimental transmissions from tomato to toma to plants. TYLCV-S was confirmed to be transmitted in a persistent, ci rculative 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 A AP. Both acquisition and inoculation feeding times influenced the dete cted 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 trans mission in serial transfer transmission tests with individual females. No significant difference in transmission efficiency was detected bet ween two colonies of B. tabaci, one inducing typical silverleaf sympto ms on squash, the other inducing only mild symtoms with more than 50 w hiteflies per plant. The phenomenon of periodic acquisition was not un equivocally proved for TYLCV-S.