To investigate whether ethylene is involved in tomato plants in response to the invasion of viroid, tomato cv. Pearson and its ethylene-insensitive mutant Never ripe (Nr) was challenged with Tomato chlorotic dwarf viroid (TCDVd). Both Pearson and Nr plants developed various symptoms including dwarf, bunch, reduced leaf size, leaf chlorosis, and necrosis at 3-wk-post-inoculation and thereafter even though the stunting in Nr was not as severe as in Pearson plants. The sizes of fruits were also significantly reduced in the viroid-infected plants. Treatments of Pearson with ethephon, an ethylene- ...
