Sequencing of small RNAs in different leaf tissues of symptomatic ASBVd-infected trees
Avocado sunblotch viroid (ASBVd) is the causal agent of avocado sunblotch disease - characterised by the formation of distinct chlorotic lesions on fruits, leaves and stems of infected trees. The mechanism by which ASBVd triggers chlorotic symptoms is unknown, though studies of related viroids (inciting similar symptoms in host plants) have shown that leaf chlorosis is linked to the RNA-silencing of specific host genes, guided by viroid-derived small RNAs (vd-sRNAs). To investigate whether the same process may be involved in eliciting bleached leaf symptoms in sunblotch-affected trees, we used sRNA sequencing to discover vd-sRNAs produced from ASBVd in planta. Bleached and asymptomatic leaves were collected from four symptomatic avocado trees, and sRNAs were sequenced from asymptomatic leaves and from green and yellow tissues of bleached leaves, respectively.