H Darmency

Backcrosses to Brassica napus of hybrids between B. juncea and B. napus as a source of herbicide-resistant volunteer-like feral populations.

Introgression between genetically modified (GM) crops and wild relatives is considered to potentially modify the genetic background of the wild species. The emergence of volunteer-like feral populations through backcross of hybrids to the crop is also a concern. The progeny of spontaneous hybrids between mutant herbicide-resistant oilseed rape (Brassica napus) and wild B. juncea was obtained. Parents, F(2) and BC(1) to B. napus were planted together in the field so as to study their performance. The chromosome number of BC(1) followed a Normal distribution. Mendelian ratio of the herbicide-resistance gene was found. The F(2) produced less seeds than B. napus, and BC(1) had intermediate production. Herbicide-resistant BC(1) were not different of their susceptible counterparts for plant weight, seed weight and seed number, but most of them exhibited B. napus morphology and larger flowers than the susceptible BC(1). They displayed an important genetic variability allowing further adaptation and propagation of the herbicide-resistance gene. Pollen flow to susceptible plants within the mixed stand was observed. As a consequence, the resistant BC(1) produced with B. napus pollen could frequently occur and easily establish as a false feral crop population within fields and along roadsides.

The effect of Bt-transgene introgression on plant growth and reproduction in wild Brassica juncea

This study aims to investigate the relative plant growth and reproduction of insect-resistant and susceptible plants following the introgression of an insect-resistance Bt-transgene from Brassica napus, oilseed rape, to wild Brassica juncea. The second backcrossed generation (BC2) from a single backcross family was grown in pure and mixed stands of Bt-transgenic and non-transgenic siblings under two insect treatments. Various proportions of Bt-transgenic plants were employed in mixed stands to study the interaction between resistant and susceptible plants. In the pure stands, Bt-transgenic BC2 plants performed better than non-transgenic plants with or without insect treatments. In mixed stands, Bt-transgenic BC2 plants produced fewer seeds than their non-Bt counterparts at low proportions of Bt-transgenic BC2 plants in the absence of insects. Reproductive allocation of non-transgenic plants marginally increased with increasing proportions of Bt-transgenic plants under herbivore pressure, which resulted in increased total biomass and seed production per stand. The results showed that the growth of non-transgenic plants was protected by Bt-transgenic plants under herbivore pressure. The Bt-transgene might not be advantageous in mixed stands of backcrossed hybrids; thus transgene introgression would not be facilitated when herbivorous insects are not present. However, a relatively large initial population of Bt-transgenic plants might result in transgene persistence when target herbivores are present.

Abscisic-acid in triazine-resistant and susceptible poa annua

Abstract Abscisic-acid (ABA) content in leaves and seeds were determined in two reciprocal hydbrids of cross between a triazine-resistant and a susceptible Poa annua . ABA in leaves appeared to be regulated by at least one major nuclear allele whilst ABA content in seeds appeared to maternally segregate with the cytoplasm. The lower ABA content found in seeds of the resistant parent and the resistant hybrid could be a secondary effect of the mutation that confers the resistance to the triazines.

Management of herbicide-resistant weed beet: a simulation study.

The rapid evolution of economie and environmental constraints on farming systems require cropping systems design or assessment to be conducted in the context of market instability as well as economie (c.g. CAP in EU) and environmental policy changes. The Nitrate Directive (91/676/EC) is one of the oIdest EU environmental policy, designed to reduce water pollution by nitrate from agricultural sources, through a set of measures, defined at regional level, and mandatory for farmers of vulnerable zones.