ARS | Publication request: AN UNUSUAL STRAIN OF ALFALFA MOSAIC VIRUS DETECTED IN CROTALARIA SPP. GERMPLASM IN GEORGIA

Submitted to: Plant Pathology Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 4, 2006
Publication Date: September 1, 2006
Citation: Gillaspie Jr, A.G., Barkley, N.L., Morris, J.B. 2006. An unusual strain of alfalfa mosaic virus detected in crotalaria spp. germplasm in georgia. Plant Pathology Journal 5(3): 397-400.

Interpretive Summary: As plant germplasm is being regenerated at the Griffin, GA germplasm maintenance site, the appearance of possible disease symptoms is monitored to prevent new viruses from entering the U.S. Viruses isolates from Crotalaria (rattlepod or sunn hemp) produced unusual symptoms on Nicotiana benthamiana assay plants. These isolates were checked by serology and found to contain a virus that reacted with alfalfa mosaic virus (AIMV) as well as combinations of other viruses. After the isolates had been transferred from N. benthamiana plant to plant about twenty times, only the AIMV could be detected by serology and the virus still produced the same symptoms on Crotalaria and N. benthamiana. A nucleic acid test (RT-PCR) followed by DNA sequencing of the expected product along with the serological tests indicate that the virus is a strain of AIMV and that it may be a new strain. Care is being taken to prevent this strain from entering the growing areas.

Technical Abstract: Virus isolates from Crotalaria species in germplasm regeneration plots in Griffin, GA were found to produce an unexpected wilting and necrosis on Nicotiana benthamiana. DAC-ELISA tests produced positive results for alfalfa mosaic virus (AIMV) and a mixture of viruses, including cucumber mosaic, blackeye cowpea mosaic, peanut stunt, and white clover mosaic viruses. After serial transfer using N. benthamiana in the greenhouse, then inoculated to healthy Crotalaria and symptomatic plants then assayed on test host plants, only AIMV could be detected by DAC-ELISA while the wilting and necrosis symptoms remained. In addition, RT-PCR tests produced products of the expected size with the Crotalaria isolate RNA as it did with a known isolate of AIMV. The band from the Crotalaria isolate was sequenced and found by BLAST search to be 92-99% identical to ten known strains of AIMV. These results indicate that the Crotalaria isolate is an AIMV strain and possibly a new strain.