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In this study, we examined the population structure and genetic diversity of Citrus psorosis virus (CPsV) in Morocco. Analysis of the coat protein partial sequences of 34 isolates collected in the three main citrus-growing areas of Morocco showed that CPsV grouped in three major groups, with low within-group nucleotide diversity. Analyses indicated that CPsV genetic diversity is not structured by the geographic origin of the CPsV isolates. The genetic variation resulting from mutations depends on evolutionary forces that have contributed to the shaping of the genetic structure and diversity of the CPsV populations analyzed here: negative selective pressure for amino acid variation, recombination between variants or mixed infection, genetic drift induced by the founder effect associated with the transmission process, and migration explained by the exchange of infected propagative plant material.

We report an improvement of a one-step reverse transcription polymerase chain reaction (RT-PCR) assay for the detection of Citrus psorosis virus (CPsV; genus Ophiovirus) in citrus trees. Two different sample preparation procedures were compared. The data showed that when using total RNA extracted by the Qiagen procedure more virus isolates could be detected compared with the Trizol procedure. Three pairs of primers reported in literature and selected within the coat protein (CP) region of the virus were used for a reliable detection of CPsV. Only one primer pair has been able to detect all CPsV isolates collected from different citrus regions of Morocco. In addition, this report showed that one-step RT-PCR was more sensitive and more consistent than ELISA test. Notably, 15 out of 22 samples tested positive by one-step RT-PCR could not be detected by Mab Ps29, thus providing a degree of differentiation among isolates. The detection protocol described in this study could be used in citrus certification programs and to test trees in nurseries and commercial orchards for CPsV infection.

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