Harmonisation of Regulatory Oversight in Biotechnology Safety Assessment of Transgenic Organisms in the Environment, Volume 5..

II.3. BRASSICA CROPS (BRASSICA SPP.) – 203

plot trials with isolation distances of over 30 m tend to be lower than those recorded in

larger scale investigations where the area devoted to the pollen donor are substantially

greater (Table 3.7).

Table 3.7. B. napus to B. napus outcrossing rates, by isolation distances, reported

from small plot trials and/or large fields

Isolation

distance

Small plot trials Large field trials (0.05 ha or more)

% outcross Reference % outcross Reference

30-60 m 0-0.0003

0.022

0.11-0.16

0.02-0.24

0.05-0.33

2.1

0.02

0.05

0

0.02-0.05

0.33

Scheffler, Parkinson and Dale (1993)

Manasse and Kareiva (1991)

Sweet et al. (1999a)

Monsanto¹

Simpson et al. (1999) (MS)

Stringam and Downey (1982)

Staniland et al. (2000)

Von Ernst et al. (1998)

Lavigne et al. (1998) (MS)

Wilkinson et al. (1995) (MS)

Ramsay, Thompson and Squire (2003)

<0.01

0.1

0.2

0-0.4

0.1-0.65

0.02

<1

0.05

0.1-0.08

0.2-0.4

0.00-0.09

Champolivier et al. (1999)

Simpson²

Beckie, Hall and Warwick (2001)

Downey (1999a, 1999b)

Norris²

Ramsay, Thompson and Squire (2003)

CETIOM (2000)

Wilkinson et al. (1995)

Dietz-Pfeilstetter and Zwerger (2004)

Weekes et al. (2005)

Rieger et al. (2002)^3

90-150 m 0.01-0.02

0.00-0.07

0.11-0.22

0.01-0.13

0.01-0.21

0.5

Manasse and Kareiva (1991)

Kamler (2000)

Simpson et al. (1999)

Simpson² (FB)

Monsanto¹

Timmons et al. (1996) (MS)

0.05

0.1

0.15

0.25-0.5

<0.5

0.01-0.02

Simpson²

Downey (1999a, 1999b)

Beckie, Hall and Warwick (2001)

Norris²

CETIOM (2000)

Weekes et al. (2005)

175-225 m 0.02-0.03

0.017-0.6

0-0.9

0.15

0.21

Simpson² (FB)

Dietz-Pfeilstetter et al. (1998)

Monsanto¹

Scheffler, Parkinson and Dale (1995)

Ramsey, Thompson and Squire (2003)

(MS)

<0.1-0.2

0.2

0.02

0.00-0.005

Norris²

Beckie, Hall and Warwick (2001)

Ramsay, Thompson and Squire (2003)

Rieger et al. (2002)^3

360-400 m 0.0038

0.06

0.6

0.0

3.7

Scheffler, Parkinson and Dale (1995)

Simpson² (FB)

Stringam and Downey (1982)

Monsanto¹

Timmons et al. (1996) (MS)

0.1

0.14

0.00-0.025

CETIOM (2000)

Beckie, Hall and Warwick (2001)

Rieger et al. (2002)^3

500-800 m 0.02-0.1 Ramsey, Thompson and Squire (2003)

(MS)

0.00-0.053

0.001-0.03

Ramsay, Thompson and Squire (2003)

Rieger et al. (2002)^3

Notes: 1. Cited by Salisbury (2002). 2. (FB) indicates use of fertile bait plants, cited by Easthan and Sweet
(2002). 3. Ranges estimated from published graph. (MS) indicates the use of male sterile bait plants.

Crawford, Squire and Burn (1999) estimated that a square donor plot of at least

400 m^2 would be needed if a sharp decline in the effectiveness of donor pollen is to be

avoided. Positioning of the donor and recipient fields can also affect the outcrossing

measurements. Ingram (2000) noted that the rate of outcrossing would be higher when the

long sides of donor and recipient fields faced each other. Hüsken and Dietz-Pfeilstetter

(2007) statistically analysed published outcrossing results for both continuous and

discontinuous designed studies. Their data indicate that with the discontinuous design, the

mean outcrossing rate between B. napus fields at 50 m and 100 m would be 0.11% and at

200 m, 0.05% with lower rates for the continuous design studies (Table 3.8).

Under short isolation distances, surrounding the pollen source with a synchronous

flowering recipient border may be effective in reducing pollen outflow (Staniland et al.,

2000; Reboud, 2003). Staniland et al. (2000) found that surrounding a spring B. napus

pollen donor with a 15 m and 30 m wide B. napus border/pollen trap, separated from the

pollen donor by a cultivated 1.5 m strip, reduced the outcrossing level to 0.02% at 30 m,