TOMATO YELLOW LEAF CURL VIRUS-DNA IN CALLUS-CULTURES DERIVED FROM INFECTED TOMATO LEAVES

Callus cultures were induced from leaves of a tomato plant infected wi th tomato yellow leaf curl virus (TYLCV) and analyzed for viral DNA pr esence during succcessive subcultures. No TYLCV DNA was detected in ca lli sampled after eight months of culture. Considerable differences in the presence of TYLCV DNA were found within sectors of a callus cultu re and between different callus cultures, throughout the entire eight months period. Infected calli which were cultured at sub-optimal tempe rature (15 degrees C) retained the viral DNA longer than at 25 degrees C. The results suggested that TYLCV disappearance during callus cultu re was due to a disruption of some of the cell-to-cell connections, re sulting in islands of infected cells in the midst of uninfected tissue and/or to the competition between the rate of cell division and that of viral DNA replication.