Gene flow via seed or pollen is a basic biological process in plant evolution.
The ecological and genetic consequences of gene flow depend on the amount and direction
of gene flow as well as on the fitness of hybrids. The assessment of potential risks
of transgenic plants should take into account the fact that conventional crops
can often cross with wild plants. The precautionary approach in risk management
of genetically modified plants (GMPs) may make it necessary to monitor significant
wild and weed populations that might be affected by transgene escape. Gene flow is
hard to control in wind-pollinated plants like beet (Beta vulgaris). In addition,
wild beet populations potentially can undergo evolutionary changes which might expand
their geographical distribution. Unintended products of cultivated beets pollinated
by wild beets are weed beets that bolt and flower during their first year of planting.
Weed beets cause yield losses and can delay harvest. Wild beets are important plant
genetic resources and the preservation of wild beet diversity in Europe has been
considered in biosafety research. We present here the methodology and research approaches
that can be used for monitoring the geographical distribution and diversity of Beta
populations. It has recently been shown that a century of gene flow from Beta vulgaris
ssp. vulgaris has not altered the genetic diversity of wild Beta vulgaris
L. ssp. maritima (L.) Arcang. in the Italian sugar beet seed production area.
Future research should focus on the potential evolution of transgenic wild beet
populations in comparison to these baseline data. Two monitoring models are presented
describing how endpoints can be measured: (1) “Pre-post” crop commercialization against
today's baseline and (2) “Parallel” to crop commercialization against GMP free reference
areas/populations. Model 2 has the advantage of taking ongoing changes in genetic
diversity and population dynamics into account. Model 1 is more applicable if gene flow
is so strong that most areas/populations contain GMPs. Important traits that may change
the ecology of populations are genes that confer tolerance to biotic and abiotic stress.
An assessment of environmental effects can realistically only be based on endpoints
and consequences of gene introgression, which may include economic values of biodiversity
in littoral and other ecosystems containing wild beet. In general, there is still a great
need to harmonize worldwide monitoring systems by the development of appropriate methods
to evaluate the environmental impact of introgressed transgenes.