Journal or Publishing Institution: Annals of Applied Biology
Date of Publication: 12/01/1996
Study: https://web.archive.org/web/20170827162218/http://www.isb.vt.edu/brarg/brasym95/brown95.htm
Author(s): Brown, J., and Brown, A.P.
Article Type: Peer Reviewed Study
Abstract:
Brassica species are particularly receptive to gene transformation techniques. There now exist genetically engineered canola genotypes with resistance to glyphosate, sulfonylurea or glufosinate herbicides. The main concerns of introducing herbicide resistant cultivars into commercial agriculture are: i. these crops will become difficult to handle volunteer weeds in following crops and ii. introgression of the engineered gene into related weed species. A survey of northern Idaho and eastern Washington showed that a number of weeds closely related to cultivated canola, wild mustard (B. kabel (DC) L.C. Wheeler), tumble mustard (Sisymbrium altissi,u, L.), birdsrape mustard (B. rapa L.), flixweed (Descurainia sophia L.), black mustard (B. nigra L.) and field pennycress (Thiaspi arvense L.) all bloom simultaneously with canola crops. In 1993 and 1994, a field study to investigate pollen movement and cross-pollination between herbicide resistant canola and non-resistant canola was carried out at two locations in Northern Idaho. In these studies, glufosinate resistant canola lines were planted in the center of a 62 m, square border, of non-resistant canola. The non-resistant border was made up with a mixture of three canola cultivars (`Westar’, `Legend’ and `Helios’) each with a different flowering time in order to ensure synchrony of flowering with the resistant center and non-resistant border. Seed was collected from the susceptible border every 1.5 m along 16 rays spaced 22.5° apart. Each ray was 26 m long. Each sample was threshed separately and the seedling progeny screened for herbicide resistance (any resistant plants being the result of hybridization with resistant plants from the center plot). A second field study was carried out at two locations to determine the frequency of natural pollination that may occur when herbicide (glufosinate) resistant canola plants are grown in close proximity to local weeds. Each of three weed species (wild mustard, black mustard and birdsrape mustard) were examined in plots with a 1:1 mixture of weed and transgenic herbicide resistant canola. At harvest, weed plants and canola plants were separated by hand and the seed from each threshed separately. All weed seeds collected were screened for herbicide resistance (resulting from interspecific crossing). In a greenhouse study, canola was used as both male and female parents in crosses to the same three related weed species. After pollination, pollen grain germination, pollen tube development, fertilization, embryo and endosperm development were monitored on each of the 64 possible cross combinations (including selfs) over time. The potential of backcrossing, after initial hybrids are created, was also investigated in the greenhouse. Findings from these studies will be used in conjunction with field studies to develop simulation models of what may happen in nature. From the preliminary results it is difficult to make strong conclusions. However some indications already observed are: i. canola seed can be readily transported throughout a region and therefore there is a risk that these crops will become volunteer weeds; ii. canola pollen can move more than 26 m and movement is affected by wind direction; iii. canola and some related weeds can combine to produce hybrid plants under glasshouse and possibly field conditions; iv. herbicide resistance is expressed in the hybrid; and v. bridge crosses could play a major role in the movement of herbicide resistant genes into the natural weed population.
Keywords: Brassica species, transgenic crops, herbicide resistance, gene transfer, herbicides, pesticides canola, greenhouse study
Citation:
Brown, J., and Brown, A.P., 1996. Gene transfer between canola (Brassica napus L. and B. campestris L.) and related weed species. Annals of Applied Biology, 129(3), 513-522.
Category:
- Environmental effects
- Pesticide use
Record ID: 265
