ABSTRACT
Transgenic plants of cotton, Gossypium hirsutum L., that carry a modified insect-control protein from Bacillus thuringiensis subsp. kurstaki (Berliner), are highly resistant to several lepidopteran insects. The objective of this study was to determine whether the introduced gene (Bt gene) affected yield, primary yield components, other agronomic properties or fiber quality. In 1990, we grew Coker 312 (the parental cultivar of the transgenic lines), MD 51 ne, a nectariless, locally adapted cultivar, and five transgenic lines in a replicated experiment at Maricopa, AZ. In 1991, we grew the same two control cultivars and four transgenic lines (two from 1990 and two new ones) at the same location. Some general trends were noted among the transgenic lines for agronomic and fiber properties, but there were notable exceptions for each property measured. The transgenic lines yielded 87 to 128% as much lint as Coker 312 and 82 to 107% as much as MD 51 ne. Among the primary yield components, the general trend among the transgenic lines was to have more lint per seed, fewer seeds per boll, and more bolls per plant than the controls. For other agronomic properties, the transgenic lines had less seedcotton per boll, lower to higher lint percentages, and higher seed weight than the control cultivars. One transgenic line was earlier (a higher percentage of lint yield at first bar-vest) than Coker 312, itself an early cultivar compared with the full-season MD 51 ne. Fiber length varied from the same to longer when compared with Coker 312, and shorter to longer when compared with MD 51 ne. Fiber strength and elongation were the same to higher in the transgenic lines than in Coker 312, but lower or the same as in the high-fiber strength MD 51 ne. Micronaire tended to be high in the transgenic lines. The most remarkable finding was that the transgenic lines showed considerable variability for all the agronomic and fiber properties measured. Insertion of the Br gene into the genome did not cause any profound deficiencies in agronomic or fiber properties. Quite the contrary, among the small sample of transgenic lines evaluated, the best one yielded significantly more lint than did Coker 312, and yielded as much lint and had fiber that was longer and just as strong as in the adapted control cultivar, MD 51 ne.
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