Interference Between Two Strains of Bean Common Mosaic Virus is Accompanied by Suppression of Symptoms Without Affecting Replication of the Challenging Virus

Abstract

An unusual type of interference between two strains of bean common mosaic virus, viz. NY15 and NL3, infecting bean plants, was investigatred. Wdhen a primary leaf was inoculated with NY15 as inducer and 1–8 days later, the opposite leaf with NL3 as challenger, the plant did not develop symptoms characteristic of NL3, i.e. systemic necrosis in the top, stem and wilting and withering of the youngest trifoloclate leaves. A7‐h interval between the inoculations with inducer and challenger already sufficed to reduce the number of plants showing NL3 symptoms. Surprisingly, the amount of NL3 in the challenge‐inoculated leaf was always than that in the singly infected control, Furthermore, NY15 could not be detected in the opposite leaf until 8 days post‐inoculation and appered enen later in that leaf when challenge‐inoculated. Histological studies showed that NL3 appered later in the xylem of bothe the petiole and stem between primary leaves and first trifoliolate leaf, as compared with the singly inoculated control. The results suggest that suppression of Nl3 symptoms by Ny15 is not caused by impeding its multiplication, but by delaying the transport of NL3 to the xylem of petiole and stem.

Analysis of the systemic colonization of cucumber plants by Cucumber green mottle mosaic virus

“…Although not a clear indicator of a role for xylem in systemic movement, localization of virus particles in the xylem has been reported in many instances (e.g. Dubois et al, 1994;Fribourg et al, 1987;Khan et al, 1994; Urban et al, 1989;Verchot et al, 2001). Further evidence supporting xylem transport has been reported in a few instances (Dubois et al, 1994;Opalka et al, 2000; Schneider & Worley, 1959a, b).…”

“…Xylem localization of virus particles has been reported for a number of viruses and hosts (e.g. Fribourg et al, 1987;Khan et al, 1994;Robertson & Carroll, 1989;Russo et al, 1967;Urban et al, 1989). Also, virus particles were recovered from guttation fluid in cucumber plants infected with 12 different viruses including CGMMV (French & Maureen, 1999).…”

Distribution and localization of bean common mosaic virus and bean black root virus in stems of doubly infected bean plants

“…An unusual type of interference between mosaic-inducing strain NY15 of BCMV and necrosis-inducing strain NL3 of BBRV has been described [4]. It was demonstrated that plants of Phaseolus vulgaris 'Bataaf' inoculated first on one primary leaf with strain NY15, as inducer, and after one or more days on the opposite leaf, with strain NL3 as challenger, did not show symptoms characteristic of the latter strain, viz.…”

“…Histological studies on immunostained, thick sections of primary leaves, petiole and stem part between primary leaves and first trifoliolate leaf of doubly infected plants had shown that strain NL3 appeared later in the xylem of both petiole and stem, as compared with the singly inoculated control [4]. Such delayed appearance of NL3 in the xylem of stem parts of doubly infected plants might be due to either a lower viral content in these plant parts as a result of hampered transport from the primary leaves, or a different distribution of the virus in this part of the plant as compared to the singly inoculated controls.…”

“…Whereas in the earlier localization studies [4] emphasis had been on the events in primary leaves (mesophyll, petiole) with only a cursory touch on those in the stem, using immunostaining technique, the present study has focussed on the accumulation and localization of the two viruses in the lower stem part, the latter being the direct link between primary leaves and first trifoliolate leaf. Presence of the viruses was established by dot-blot immunoassay and, besides the immunostaining technique for initial screening to localize at tissue level, the immunogold-silver staining was used for exact cellular localization of viral antigen.…”