Molecular identification and characterization of iris yellow spot virus (IYSV) and garlic virus X (GVX) infecting Allium species

Allium species, such as Onion (Allium cepa L.) and garlic (Allium sativum L.), have been cultivated worldwide for centuries due to its enormous medicinal uses as well as for cooking practices. A large number of RNA viruses have been known to cause significant yield losses and also adversely affect the quality of Allium species. Among them, iris yellow spot virus (IYSV) and associated garlic virus X (GVX) from tospovirus family cause huge number of yield losses in onion and garlic crop. The disease due to IYSV and GVX was recorded in different locations on the basis of their characteristic symptoms. Experiments revealed that IYSV has the ability to transmit mechanically in a very efficient manner while the dispersal of GVX was only limited through its vector as compared to mechanical transmission. The disease incidence of IYSV on onion was reported about 80% while 2% of GVX was reported on garlic by mechanical transmission. Result revealed that IYSV is more viruliferous and has the ability to transmit more efficiently on onion as compared to GVX on garlic. PCR amplified IYSV samples of approximately 800 base pairs (bps) product using specific primer targeting coat protein (Cp) region, whereas no amplicon was detected for GVX infected samples. Phylogenetic analyses of 2 isolates RP13PK and RP27PK have shown 99.3% homogeneity with isolate DQ233469 as compared to remaining isolates. Therefore, the findings indicate that IYSV is a highly variable virus, undergoing rapid evolution in the region, necessitating vigilant monitoring and effective management. The outcomes imply that greater caution is required for controlling IYSV compared to GVX. Disease management strategies should be formulated with careful consideration of the swift evolution patterns exhibited by IYSV.