Skip to main content
SLU publication database (SLUpub)

Research article2004Peer reviewed

Detection of a natural point mutation in Potato virus A that overcomes resistance to vascular movement in Nicandra physaloides, and studies on seed-transmissibility of the mutant virus

Rajamaki ML, Valkonen JPT


Isolate M of Potato virus A (PVA-M; genus Potyvirus) is avirulent in Nicandra physaloides L. (family Solanaceae). The inoculated leaves are infected but no systemic infection is observed. Forty plants of 'Black Pod' (BP) and 'Black Pod Alba' (BPA), two variants of N. physaloides described in this study, were inoculated with PVA-M. Two plants of BP and one plant of BPA were systemically infected. Mosaic, blistering and dark green islands developed on the systemically infected leaves, and flowers showed colour-break symptoms. PVA progeny were sequence-characterised for the 6K2 protein and viral genome-linked protein (VPg) encoding regions known to control the long distance movement of PVA in N. physaloides. All virus progeny (designated as PVA-Mm) in the systemically infected leaves of the plants inoculated with PVA-M contained only a single amino acid substitution (Val116Met) in the central part of VPg due to a nucleotide substitution G6033A, as compared to PVA-M. Other PVA isolates that infected N. physaloides systemically also contained Met 116 in VPg. In a previous study using chimeric viruses, Met116 in VPg was shown to be a major determinant for vascular movement of PVA in N. physaloides, and this study reveals that the mutation for Met116 can occur in vivo during replication of the avirulent PVA-M in infected plants. Immunolocalisation studies on BP and BPA plants showed that the pods (berries) and seed coat contained PVA-Mm in the developing seeds, but no virus was detected in embryons. Up to 27% of the mature seeds contained PVA-Mm but no transmission to seedlings was observed in a total of 450 seeds tested, and no test plants were infected following mechanical inoculation with extracts prepared from the seeds

Published in

Annals of Applied Biology
2004, Volume: 144, number: 1, pages: 77-86

    UKÄ Subject classification

    Agricultural Science

    Publication identifier


    Permanent link to this page (URI)