Effects of two naturally occurring mild potyviruses on the symptom expression of vanilla necrosis potyvirus in Vanilla fragrans

Two mild potyviruses isolated from Vanilla fragrans in Tonga were evaluated for their ability to protect V. fragrans against the severe effects of van illa necrosis potyvirus (VNV). Plants infected with the mild strain were mu ltiplied in vitro and after establishment in pots in the glasshouse were ch allenged with VNV. The symptoms of V1 and V3 infection of V. fragrans are d escribed and the effects of V1, V3, and VNV on the growth of V. fragrans qu antified. Both mild strains moderated the effects of VNV, demonstrating the general potential for using in vitro produced mild strain protected plants for the control of VNV. However, these particular strains also reduced pla nt growth in the absence of VNV.