Evaluation of transgenic cotton lines tolerant to glufosinate, bromoxynil, and both glufosinate and bromoxynil

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Title: Evaluation of transgenic cotton lines tolerant to glufosinate, bromoxynil, and both glufosinate and bromoxynil
Author: Becker, William David
Abstract: The adoption of weed control systems that use biotechnology -derived , herbicide -tolerant crops has increased rapidly since their commercial introduction in 1997 . The limited availability of effective , broad -spectrum , post -emergence herbicides has been a contributing factor in the widespread use of these weed control systems in cotton production . The prospect of multi -transgene -stacking of herbicide tolerances provides opportunities for improved weed resistance management , enhanced weed control , increased flexibility , and decreased weed control costs . Cotton varieties have been previously developed that are tolerant to bromoxynil or glufosinate -ammonium . For the purposes of this study , experimental cotton lines were developed that are tolerant to bromoxynil or glufosinate -ammonium and to both bromoxynil and glufosinate -ammonium . The lines were developed in order to evaluate the effects of the bxn and fcar genes singularly and in combination on cotton growth , agronomic characteristics , and fiber properties . Four crosses were made between a bromoxynil -tolerant cotton line and plants from a glufosinate -ammonium -tolerant population . F2 derived lines were developed from each of these crosses that express either : (1 ) bromoxynil tolerance , (2 ) glufosinate -ammonium tolerance , (3 ) tolerance to both herbicides , or (4 ) no herbicide tolerance . Sixteen treatments (four crosses and four herbicide traits ) were evaluated in a randomized complete block design with a factorial arrangement of treatments . The trials were conducted over two years , with one location being used in 2002 and three locations being used in 2003 . There were no significant main effect differences observed among herbicide traits for either year , except for maturity across locations in 2003 , and plant height in one location in 2003 . Results from the 2002 experiment showed significant interaction effects between cross and herbicide trait for storm resistance , plant height , and lint percentage , as well as the fiber properties of length , strength , micronaire , and uniformity . The 2003 results showed a significant interaction effect across locations between cross and herbicide trait for storm resistance , lint percentage , lint yield , fiber length , strength , micronaire , and uniformity . The inconsistent differences observed over crosses among herbicide traits for each of the characteristics evaluated may be due to a relatively small effect of the expression of the herbicide tolerance genes when compared to the inherent variation typically observed in F2 derived cotton lines . The variation observed in each of the characteristics evaluated , among the experimental lines , was within the normal range of what would be expected from non -transgenic cotton lines developed from F2 derived cotton populations . Thus , the expression of the bar and bxn genes singularly or in combination in these tests did not substantially affect cotton growth , agronomic characteristics , or fiber properties . Transgene efficacy tests using experimental lines tolerant to both bromoxynil and glufosinate -ammonium showed no detrimental effects on early season cotton growth when both herbicides were applied in combination .
URI: http : / /hdl .handle .net /2346 /20350
Date: 2004-08

Citation

Evaluation of transgenic cotton lines tolerant to glufosinate, bromoxynil, and both glufosinate and bromoxynil. Doctoral dissertation, Texas Tech University. Available electronically from http : / /hdl .handle .net /2346 /20350 .

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