Development of transgenic crops and their risk assessment

الملخص EN

Aphid transmitted viruses are the primary cause of potato seed lots being rejected or downgraded for recertification.

Farmers tend to consider insecticides their primary defense against current season spread of potato viruses in seed potatoes, but their use is of inconsistent benefit.

Insecticides can interrupt PLRV spread from within field sources because of the extended post-acquisition latent period of this persistently transmitted virus.

However, winged viruliferous aphids generally are not killed quickly enough to prevent PLRV spread even when aphidicidal residues are present.

All other aphid-transmitted potato viruses are transmitted non-persistently and can be acquired and transmitted in feeding probes of seconds, making insecticides of little benefit.

Non-chemical control alternatives to virus control include strategies to reduce infection exposure, e.g., limited generation seed increase, summer field inspections and rouging to eliminate within field sources of virus inoculums, off-season grow outs of representative sub-samples of seed lots and decertification of those above virus incidence thresholds, spatial isolation of seed production from virus sources and severe vector pressure, temporal avoidance of vectors including early vine kill and environmental manipulations to reduce vector numbers.

Floating row covers can be used to protect early generation seed increase.

Planting crop borders around seed fields, 3-m wide is sufficient, and achieving uniform stands to minimize within field plant apparentcy to winged aphids can effectively limit vector colonization.

Use of agricultural oils can limit spread of non-persistent viruses such as PVY, while insecticide applications targeted to field margins at the onset of colonization events can greatly reduce insecticide use and costs, while preserving natural enemies.