1): (i) DP group I: includes TM-1, DP 458BR, DP 555BR, and SG 125BR; (ii) DP group II: includes DP 491 and DP 449BR; (iii) ST group: includes ST 5599BR, ST 457, BXN
49B, ST 4892BR, ST 580, and ST 4793R; (iv) FM group: includes FM 989, FM 989BR, FM 991R, and STX 0003; (v) Acala group I: includes Acala 1517-95, 1517-99, and Acala 1517-03; (vi) Acala group II: includes PHY 78 and Acala 1517-02; (vii) Acala PHY 72; (viii) NX 2419; and (ix) All Tex Atlas.
Commercial fields in the San Joaquin Valley neighboring either Roundup Ready or BXN cotton were sampled at distances between 25 m and 1625 m (1 mile) from the herbicide-resistant pollen source.
Samples from commercial fields adjacent to BXN cotton were bioassayed in the same way.
Seventy random seedling samples were tested by polymerase chain reaction (PCR) for the presence of the BXN transgene for 2001 field trials and 169 seedling samples were tested from the 2002 trials at Emergent Genetics (Scott, MS) using proprietary primers.
Being a selective, contact herbicide, production of BXN cultivars typically includes use of the soil-applied herbicides (pendimethalin [N-(1-ethylpropyl)-3,4-dimethyl-2,6-dinitrobenzenamine] or trifluralin [2,6-dinitro-N,N-dipropyl-4-(trifluoromethyl) benzenamine], applied at or before planting, followed by over-the-top bromoxynil applications, then additional postdirected herbicides for weed species not controlled by bromoxynil (Culpepper and York, 1997, 1999).
Despite the capability to apply bromoxynil over-the-top of BXN cultivars later in crop development compared with glyphosate-resistant cultivars, glyphosate-resistant cultivars are more popular because glyphosate controls more weeds encountered in cotton production (Culpepper and York, 1999).
Except for BXN cultivars, the first wave of transgenic cultivars received little or no public testing before wide-scale grower adoption (May et al., 2000), while the particular transgenic technology itself was widely tested by entomologists and weed scientists (Benedict et al., 1996).
The excellent crop tolerance to bromoxynil in BXN cultivars and its availability in only a few cultivars has lessened concerns that OCTs do not evaluate cultivar variation in bromoxynil resistance.