GM risk assessment: Pollen carriage from Brassica napus to B. rapa varies widely between pollinators

The value of twinned pollinator-pollen metabarcoding: bumblebee pollination service is weakly partitioned within a UK grassland community

Predicting ecological impact of declining bumblebee (Bombus) populations requires better understanding of interactions between pollinator partitioning of floral resources and plant partitioning of pollinator resources. Here, we combine Cytochrome Oxidase 1 (CO1) barcoding for bumblebee identification and rbcL metabarcoding of pollen carried by bees in three species-rich UK pastures. CO1 barcoding assigned 272 bees to eight species, with 33 individuals belonging to the cryptic Bombus lucorum complex (16 B. lucorum and 17 B. cryptarum). Seasonal bias in capture rates varied by species, with B. pratorum found exclusively in June/July and B. pascuorum more abundant in August. Pollen metabarcoding coupled with PERMANOVA and NMDS analyses revealed all bees carried several local pollen species and evidence of pollen resource partitioning between some species pairings, with Bombus pratorum carrying the most divergent pollen load. There was no evidence of resource partitioning between the two cryptic species present, but significantly divergent capture rates concorded with previous suggestions of separation on the basis of foraging behaviour being shaped by local/temporal differences in climatic conditions. Considering the bee carriage profile of pollen species revealed no significant difference between the nine most widely carried plant species. However, there was a sharp, tipping point change in community pollen carriage across all three sites that occurred during the transition between late July and early August. This transition resulted in a strong divergence in community pollen carriage between the two seasonal periods in both years. We conclude that the combined use of pollen and bee barcoding offers several benefits for further study of plant-pollinator interactions at the landscape scale.

Potential for gene flow from genetically modified Brassica napus on the territory of Russia

Gene flow from genetically modified crops has been studied for more than 20 years, but public concern still remains. A lot of data on this matter is obtained on the territory of EU and the USA, but in the majority of countries, such experiments were never carried out. Here, we present the first study of interspecific and intraspecific hybridization of transgenic Brassica napus on the territory of Russia. The experiment was conducted using two different models of coexistence. Cross-pollination with related species was more frequent in mixed than that in separated populations. We observed maximum 4.1% of transgenic seeds in the progeny of Brassica rapa and 0.6% in the progeny of Brassica juncea. The highest intraspecific hybridization rate of 0.67% was observed in separated populations. DNA fragments, typical to both parents, were present in the genome of the hybrids. The risk of gene flow in Russia is relatively low, but it will be problematic to do environmental monitoring on such a big territory. However, instead of banning the cultivation of genetically modified crops, some new varieties with visually detectable selective traits could be designed and approved for cultivation.

Performance of aneuploid backcross hybrids between the crop Brassica napus and its wild relative B. rapa

Crossings between the diploid wild Brassica rapa (AA, 2n = 20) and the tetraploid cultivar B. napus (AACC, 2n = 38) can readily be made. Backcrosses to the wild B. rapa (BC₁ ) produce aneuploids with variable chromosome numbers between 20 and 29. How does survival and performance relate to DNA content of plants? Growth of the BC₁ plants was measured in the lab. One plant in the F₁ self-pollinated spontaneously and produced abundant F₂ seeds that were also examined. The number of C-chromosomes was estimated from DNA values obtained with flow cytometry. Average DNA value of the BC₁ was similar to that of the parents, which shows that C-chromosomes do not reduce success of pollen or embryos. The average DNA value in the F₂ was 13% higher than in the F₁ , suggesting that extra C-chromosomes facilitated gamete success and/or embryo survival. Under both optimal and drought stress conditions growth and survival of BC₁ hybrids was similar to that of B. rapa. No significant correlations existed between growth or survival and DNA value. Aneuploid plants were not inferior under the conditions of the growth room and may persist in nature. We discuss other factors, such as herbivory, that could prevent hybrid establishment in the field.