First report of Ageratum conyzoides L. and Sida acuta Burm F. as new weed hosts of Tomato yellow leaf curl Tanzania virus

Tomato farms in the Dodoma region of Tanzania where a high incidence of Tomato yellow leaf curl Tanzania virus has been reported were visited to survey for weed hosts. Weeds exhibiting symptoms of infection by the virus were collected and identified. Lysates of leaf samples of the weed species were prepared and clarified by centrifugation. The clarified sap was dotted on nylon membranes and hybridised with a DIG-labelled probe. The putative viral DNA was extracted from the samples by phenol-chloroform procedures, and amplified by polymerase chain reaction methods using a primer pair designed to amplify a 1.2 kb fragment of the virus. Strong hybridisation signals were observed when sap from Ageratum conyzoides and Sida acuta were hybridised to the labelled probe. Similarly, the expected fragment size was obtained after amplification of DNA from both samples. It is concluded that these weeds are new hosts of Tomato yellow leaf curl Tanzania virus. An extensive search for yet undiscovered weed hosts is advocated, while the practice of farm sanitation is encouraged to eliminate reservoirs of the virus and vector.