Since introduction in 1996, transgenic technology has been readily accepted in the Mid-South and Southeast regions of USA to the extent that transgenic cotton varieties now dominate the Upland cottonseed market. In 2005, Dow AgroSciences introduced the stacked, two-gene WideStrike™ Insect Protection trait. Even though the combination of Cry1Ac and Cry1F transgenes in WideStrike™ confers value-added, broad-spectrum control of lepidopteran insect pests, most cotton growers in USA rely heavily on glyphosate tolerance technology as the primary means of weed control. Consequently, the most widely planted Upland cotton varieties contain both transgenic insect protection and glyphosate tolerance traits. In 2006, Monsanto introduced the second generation of glyphosate tolerance, Roundup Ready® Flex (RF), which greatly extended the glyphosate application window over the initial Roundup Ready® trait. Within the USA, PhytoGen Seed Company is the only cottonseed company offering cotton varieties expressing the WideStrike™ trait either alone or stacked with glyphosate tolerance genes.

Two PhytoGen cotton varieties, PHY440W and PHY425RF, were developed independently by backcross breeding methodology using PSC355 as the recurrent parent. When the two varieties were initially crossed to combine WideStrike™ with Roundup Ready® Flex, fewer F2 plants were observed to be homozygous for all three transgenes than was expected. A genetic linkage study conducted in 2006 revealed that the Cry1F and Roundup Ready® Flex transgenes were linked in Upland cotton. Since the two genes are now linked in coupling in the WideStrike™/Roundup Ready® Flex donor parent, approximately 2.7x more homozygous plants are now being identified in the F2 of new conversions than is expected for 3 independent genes.

™WideStrike is a trademark of Dow AgroSciences LLC ™PhytoGen and PhytoGen logo are trademarks of PhytoGen Seed Company ®Roundup Ready Flex is a registered trademark of Monsanto Company