How Would You Test for Yield Drag or Yield Lag?
The most important hybrid quality for the farmer is yield. To them, reduction in yield caused by yield lag or yield drag has the same economic impact. Therefore the farmer would want to obtain the same performance information on a genetically engineered variety that they use to make planting decisions on non-genetically engineered varieties.
The plant breeder and genetic engineer, however, can benefit from knowing if yield drag or yield lag is a problem. Yield drag can only be measured by comparing the performance of the original elite line (isoline) with the transgenic version of that line after it has been through backcrossing.
Severe yield drag would be documented early in the evaluation of a genetically engineered crop. Genetic engineers can overcome yield drag by producing additional events with an insertion into a better chromosome location or using modified transgenes that interfere less with the development in the plant.
Yield drag is apparent when a transgenic line yields less than its isoline. Image by P. Hain
Yield lag can be measured by comparing the transgenic elite line with the latest elite line. The difference in yield potential is the yield lag.
Yield lag will be a problem as long as breeders continue to make improvements in yield and as long as the backcrossing method is an integral part of developing a genetically engineered crop.
Yield lag is apparent when a transgenic line yields less than a newly released elite line. Image by P. Hain