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The four year BRIGHT project was initiated in autumn 1998 and the research was conducted by NIAB, Broom's Barn, Rothamsted Research, Morley Research Centre and the Scottish Agricultural College (Aberdeen) in a consortium with Agrovista, BASF, Bayer, BBRO, HGCA and Monsanto sponsored by Defra and SEERAD through the Sustainable Arable LINK programme.
The BRIGHT project had the objective of determining the implications of growing HT crops both for agriculture and the environment by simulating different rotational scenarios, at a number of sites. In the BRIGHT project herbicide tolerant (HT) winter oilseed rape (WOSR) and sugar beet were grown in four year arable rotations with cereals and other crops. Cultivars of sugar beet and WOSR genetically modified to be tolerant to glyphosate and glufosinate were compared to conventional cultivars. Additionally, in years 1 and 2 a cultivar of WOSR resistant to the imidazolinone herbicides, bred by conventional breeding techniques, was compared to the other three. The research programme encompassed whole crop rotations, studying weed control in the non-HT crops as well as the HT crops. The programme included rotations that were perceived to be best practice and worst case scenarios (where potential impact of the use of HT cultivars might be expected to be highest). Thus, two included only oilseed rape or only sugar beet and one was based on a sequence of rape and sugar beet. HT crops were mainly grown twice in each rotation and all possible sequences of HT and conventional cultivars were compared.
The herbicide tolerance systems were effective and flexible, achieving similar or greater levels of weed control, compared to conventional practice, depending on site, season and other factors. The performance of the conventional and HT weed control systems rarely approached total weed control. No significant decreases in botanical (species) diversity were observed. Weed seed banks increased in both WOSR and sugar beet rotations between the start and end of the 4 year project, with no differences detected between treatments. At most sites weed control was more effective in the cereal component of the rotation than it was in the oilseed rape or sugar beet.
Seed banks of volunteer oilseed rape seed left in the field after harvest initially declined rapidly but then persisted at moderate levels with little apparent difference between WOSR varieties. The field studies and Petri-dish tests confirmed that the HT cultivars were no more persistent than the conventional cultivar (Apex). However, appreciable numbers of seeds remained in the seed bank at some sites up to 3 years after the harvest of the WOSR crops.
No direct impact of the transgenes themselves or the transgenic crops on crop production and botanical diversity was observed in these experiments. The only differences observed were due to the different herbicide programmes.
Outcrossing between oilseed rape varieties declined with increasing distance between plots and resulted in combined herbicide tolerance in some instances. Levels of outcrossing matched those reported in other studies in the UK.
Herbicide tolerance in WOSR and sugar beet increased options for the control of weeds in these crops. They gave greater flexibility of timing and management. In most rotations they had little effect on weed management in subsequent crops. However when the same HT was used in sugar beet, following HT WOSR, additional herbicides were needed to control volunteer rape.
The use of HT crops reduced the amount of herbicide active ingredient applied to sugar beet. In both crops the costs of glufosinate, and particularly glyphosate were lower than those of conventional broad-leaved weed and graminicide treatments. Other advantages were greater control of weeds closely related to the crops which are more difficult or expensive to control (e.g. weed beet in sugar beet).
Data from BRIGHT will be used to contribute to guidelines on the management of genetically modified herbicide tolerant crops.
The report recommends further studies to refine the management of HT crops in order to achieve environmental targets as well as agronomic objectives.
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