Molecular and biological characterization of Cocadviroid rimocitri infecting pistachio (Pistacia vera L.) trees for the first time in Türkiye.

Cocadviroid rimocitri (citrus bark cracking viroid, CBCVd) diagnostic surveys were carried out from July 2022 to August 2024 in major pistachio (Pistacia vera L.) growing locations of Southeast Anatolia region (Türkiye). Dormant shoots, green twigs, and leaves were collected from a total of 223 symptomatic and asymptomatic trees in 51 pistachio orchards and tested by RT-PCR to investigate the presence of the viroid. CBCVd incidence was about 19.7% out of all tested samples. Full length sequences of CBCVd-pistachio isolates ranged from 282 to 286 nucleotides. They had considerable sequence variation, with 14 distinct haplotypes, resulting in a haplotype diversity of 0.925. Overall, the estimated average number of nucleotide differences (k) and nucleotide diversity (π) were 5.16 and 0.019, respectively. These findings indicate that the CBCVd in tested pistachio trees comprised a heterogeneous population. The nucleotide sequence homology was 96-100% among themselves, and they were most closely related to isolate W11 from pistachio (MF198463). The pathogenicity of these CBCVd-pis variants was demonstrated in cucumber seedlings, and viroid transmission to four healthy rootstocks (P. vera cv. 'Siirt,' P. atlantica, P. khinjuk, and UCB1). Symptom expression on cucumber seedlings was recorded after 20-day post-inoculation. Graft uptake was significantly reduced when viroid-infected buds were grafted onto all rootstocks.