Deep Sequencing Data and Infectivity Assays Indicate that Chickpea Chlorotic Dwarf Virus is the Etiological Agent of the "Hard Fruit Syndrome" of Watermelon

Chickpea chlorotic dwarf virus (CpCDV), a polyphagous mastrevirus, family Geminiviridae,
has been recently linked to the onset of the "hard fruit syndrome" of watermelon, first described
in Tunisia, that makes fruits unmarketable due to the presence of white hard portions in the flesh,
chlorotic mottling on the rind, and an unpleasant taste. To investigate the etiological agent of this
disease, total RNA extracted from symptomatic watermelon fruits was subjected to small RNA
sequencing through next generation sequencing (NGS) techniques. Data obtained showed the
presence of CpCDV and two other viral species. However, following validation through polymerase
chain reaction (PCR), CpCDV was the only viral species consistently detected in all samples.
Watermelon seedlings were then challenged by an agroinfectious CpCDV clone; several plants
proved to be CpCDV-infected, and were able to produce fruits. CpCDV infected and replicated in
watermelon fruits and leaves, leading to abnormality in fruits and in seed production, similar to
those described in field. These results indicate that CpCDV is the etiological agent of the "hard fruit
syndrome" of watermelon