A Description of the Possible Etiology of the Cilantro Yellow Blotch Disease.

A virus-like disease characterized by foliar yellow blotch symptoms and resembling those described for cilantro yellow blotch disease in California was observed in a 4.05-ha cilantro (Coriandrum sativum) cv. Santo field in Hidalgo County, Texas during spring 2019. Disease incidence at harvest was estimated at ∼20%, and the affected plants were rendered unmarketable. Foliar systemic chlorosis symptoms were observed on sap-inoculated Nicotiana occidentalis plants (n = 3) using inocula from symptomatic cilantro. Total RNA aliquots from 11 randomly collected leaf tissue samples (symptomatic = 7, asymptomatic = 4) were pooled into a composite cilantro RNA sample which was analyzed by high throughput sequencing (HTS). Analyses of the obtained 15.7 million raw reads (76 nt each) yielded virus-specific contigs that mapped to the genomes of alfalfa mosaic virus (AMV), beet pseudoyellows virus (BPYV), and lettuce chlorosis virus (LCV). Virus-specific primers designed from the HTS-derived sequences were used to screen the samples in two-step RT-PCR assays, resulting in the detection of AMV+BPYV in 3 of 7 symptomatic cilantro samples, AMV+LCV in 4 of 7 symptomatic cilantro samples, and AMV alone in the 4 asymptomatic cilantro and sap-inoculated N. occidentalis samples. The results represent the first reports of the natural infection of cilantro by BPYV and LCV and implicate the mixed infection of a Crinivirus and AMV in cilantro yellow blotch disease.