RESUMEN
In the years 2021 and 2022, lettuce plants showing blistering, chlorosis, mosaic, rosetting/ excess proliferation, and stunting symptoms were subjected to leaf-dip transmission electron microscopy, RT-PCR followed by sequence analysis and bio-assay to unfold the identity of associated virus(es). The association of long filamentous virions (~ 850 nm in length) as seen through leaf-dip transmission electron microscopy suggested the possible infection by a potyvirus or crinivirus, either singly or in combination. RT-PCR assays using generic primers targeting the RdRp region of criniviruses and the NIb region of potyviruses revealed the association of both a crinivirus as well as a potyvirus. The gel-purified RT-PCR products derived from the RdRp region of criniviruses upon cloning, sequencing, and NCBI BLAST analysis indicated the associated crinivirus as cucurbit chlorotic yellows virus (CCYV). Further, RT-PCR assays using specific primers targeting CP and CP minor genes of CCYV followed by cloning and sequencing confirmed its association with the diseased lettuce plants. Besides, the bioassay based on whitefly-mediated virus transmission followed by RT-PCR confirmed the infectivity of CCYV from diseased to healthy lettuce plants. The results of this study confirmed the natural infection of CCYV in lettuce host for the first time in the world indicating its distribution across the crop families.
RESUMEN
In India, cucurbit aphid-borne yellows virus, a cucurbit-infecting polerovirus, is emerging in the recent past with respect to its occurrence on different crops and geographical locations. This emphasized the need for an investigation to search for the possible occurrence of the other related species Polerovirus. In this view, different cucurbit hosts exhibiting severe chlorosis, bleaching, and yellowing symptoms were collected from the Vegetable Experimental Fields of IARI, New Delhi. The samples exhibiting yellowing and bleaching symptoms were associated with small isometric virions measuring ~ 25 nm under transmission electron microscope. The RT-PCR assays using generic (covering the partial RdRp, intergenic region and partial CP region) and complete coat protein (CP) gene-specific primers confirmed the association of a polerovirus. Further, complete CP gene sequence analyses revealed the association of a distinct species of Polerovirus with the pumpkin samples. These isolates showed the CP gene sequence identities below the species demarcation limit (90%) with the corresponding gene sequences of already reported polerovirus isolates. The results of this study provide the molecular evidence for the occurrence of a new species of Polerovirus, named tentatively as Pumpkin yellows virus (PuYV) in India.