Summary auto-generated
This 1992 study investigated resistance mechanisms to potato leafroll virus (PLRV) in potato cultivars using a double-graft sandwich technique, where stem sections from test cultivars were grafted between healthy stock plants and PLRV-infected scions to measure virus movement rates through the phloem. The researchers tested cultivars with different combinations of resistance to infection (IR) and resistance to virus accumulation (AR). They discovered that Bismark potato cultivar exhibits a specific, independent resistance to PLRV phloem transport—virus movement through Bismark stems was significantly slower than through other cultivars, regardless of their IR and AR status. This resistance operated in stems of different ages, was virus-specific (not effective against potato virus X), and was not influenced by prior PVX infection. The study also examined aphid (Myzus persicae) feeding preferences and colonization rates, finding these differed among cultivars but were unrelated to IR, AR, or phloem transport resistance. When leaves were inoculated with viruliferous aphids, systemic PLRV movement was delayed in Bismark and Omega cultivars, possibly linked to IR. The results suggest PLRV movement in plants involves multiple, independent resistance mechanisms beyond previously identified IR and AR components.
Key findings
- Bismark potato cultivar has a specific, virus-specific resistance to PLRV phloem transport independent of infection resistance (IR) and accumulation resistance (AR)
- PLRV movement through Bismark stem sections was significantly slower (22.5-33.7 days) than other cultivars tested (13.6-28.7 days)
- The phloem transport resistance in Bismark operates in stems of different ages, is not effective against potato virus X, and is unaffected by prior PVX infection
- Delayed systemic movement of PLRV from aphid-inoculated leaves in Bismark and Omega cultivars may be linked to IR but is independent of AR and phloem transport resistance
- Aphid feeding preferences and colonization rates differ among cultivars but are unrelated to IR, AR, or resistance to phloem transport
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Abstract
A double-graft sandwich technique in which sections of potato stem from different potato cultivars were grafted between a susceptible healthy stock plant and a potato leafroll virus (PLRV)-infected scion was used to study the rate of phloem transport of PLRV in cultivars differing in resistance to PLRV infection (IR) and accumulation (AR). Resistance to phloem transport (i.e. delayed PLRV systemic movement) was found in Bismark cultivar (IR AS). This was independent of IR and AR as the rate of movement in Bismark cultivar was markedly slower than that in Omega and Spunta (IR AR), Delaware (IS AR), and Desiree and Renova (IS AS) cultivars. It operated in Bismark cultivar stems of two different ages, but did not operate against potato virus X (PVX) and was not influenced by previous infection with this virus. Aphid vector (Myzus persicae) feeding preferences and colonization rates differed between cultivars, but the cultivar characteristics responsible were unrelated to IR, AR or resistance to phloem transport. Delayed systemic movement of PLRV out of leaves inoculated with viruliferous aphids was independent of AR and resistance to phloem transport, and remained unaffected by previous infection with PVX. It was also independent of cultivar factors causing different aphid feeding preferences and colonization rates, but may be linked to IR.
† Present address: New Town Research Laboratories, Department of Primary Industry, Fisheries and Energy, Hobart, Tasmania 7008, Australia.