Poster: Emerging Technologies

Abs # 895: Reproductive Tolerance to Sequential Applications of Glyphosate in Roundup Ready^® and Roundup Ready Flex Cotton

Presenter:	Mery, Ramon , rmery@mail.com
Authors	Mery, Ramon  (A)   Cothren, J. Tom  (A)   Halfmann, Shane W (A)
Affiliations:	(A): Texas A&M University, College Station, TX 77843

Roundup Ready^® technology has allowed growers to use glyphosate as part of an in-season weed control system since Monsanto™ first introduced it to the market in 1997. Nevertheless, growers and researchers have reported that off-label glyphosate applications have caused boll abscission and consequent yield reduction in Roundup Ready cotton (RRC). Further research has indicated that off-, and within-label glyphosate applications may negatively impact RRC anther development, pollen production, pollen morphology, pollen viability, and flower morphology. Therefore, the potential to interfere with pollination, fertilization of ovules, and boll development is increased when glyphosate is applied to RRC. Monsanto’s new Roundup Ready Flex™ (RR Flex) technology has been designed to enhance the reproductive tolerance to glyphosate over RRC. Greenhouse studies were conducted at Texas A&M University at College Station, TX to evaluate the performance of a RR Flex cultivar to glyphosate application, as compared with its negative isoline and a RRC cultivar. Glyphosate was sequentially applied over-the-top on both the RR Flex and RRC cultivars at a rate of 1.5 lb ae A^-1 at three different leaf stages of growth (i.e., 4-, 8-, and 12-leaf stage). Currently the label recommendation for a single over-the-top application on a conventional RRC cultivar is 0.75 lb ae A^-1 no later than the 4-leaf stage of growth. The negative isoline cultivar did not receive any glyphosate treatment for comparison purposes. Parameters examined included lint yield, fruiting distribution patterns, pollen availability, pollen viability, and flower morphology. Results of this study will be presented.