Submitted to: World Cotton Research Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: October 21, 2007
Publication Date: N/A
Interpretive Summary: This presentation and publication’s objective is to summarize the changes in Mid South cotton that have taken place in the last 20 years due to breeding. In this same session others will make similar presentations relating to their specific areas of the United States. Two major changes have occurred in cotton breeding in the Mid South in the last 20 years. First, the biggest change has been the introduction of transgenes into established varieties of cotton. A transgene is a gene that previously was not in cotton but was in some other species. Genes found in several bacteria that result in resistance to the bollworm/budworm complex and other genes that give resistance to herbicides have, through using genetic engineering technology, been transferred into conventional cotton varieties. These transgenes were first introduced into commercial cotton in 1995 and made up 0.07% of the acreage planted. In 2006, transgenic varieties were planted on 87.6% of the acreage. A comparison of transgenic insect resistant and conventional (non-insect resistant) varieties across five states and two years showed yield losses of 3.9% for the transgenics and 6.7% for the conventional varieties. The transgenics average number of insecticide applications was 4.7 and that for the conventional varieties was 5.4. The herbicide resistant cottons made weed control much simpler to manage. However, the major use of transgenics to reduce certain insects and weeds has allowed other insects, such as plantbugs and stinkbugs, and other weeds to fill the biological void. Transgenic varieties are easier to develop and many different combinations of seven transgenes have been produced to meet varying grower needs. However the insect control cost, including technology fees for transgenics is slightly 10.5% higher than that for non-transgenic varieties. Also, when transgenic and non-transgenic varieties are compared in traditional variety tests where insects are controlled with insecticides, no increase in yield and fiber quality due to transgenics are observed. The second major change in cotton as a result of breeding has been the introduction of varieties bred and developed in Australia. These varieties in 2006 accounted for 44.1% of all the USA harvested acreage. The Australian FiberMax varieties accounted for 26.7% of the total acreage and ‘DP 555BR’® accounted for 17.4% of the total acreage. The use of the FiberMax varieties resulted in a significant increase in fiber length and strength in Texas.
Technical Abstract: The objective of this presentation and manuscript is to discuss the two factors that have resulted in the most changes in the USA due to cotton breeding in the last 20 years. The biggest change brought about by cotton breeding has been the introduction of commercial transgenic cotton varieties in 1995. Their use has grown from 0.07% to 87.6% in 2006. Three transgenes that were naturally in a soil bacterium, Bacillus thuringiensis, have resulted in a significant reduction in crop losses and insecticide applications due to lepidopterous insects. The use of four herbicide resistant transgenes has made crop management much simpler. The transgenic cultivars produced from 1995 to 2006 have mostly been by the backcross breeding method. This breeding allows faster incorporation of singles genes. As a result, during the transgenic era 2.36 times more cultivars were released per year as during the five year period prior to transgenic use. When grown in a conventional cultivar management system, there has been no increase in yield or fiber quality due to transgenics. The yield and fiber quality of transgenics, when grown under this management system, are expected to be about the same as their recurrent parent, and they are. The second major change due to cotton breeding was the introduction of Australian cultivars. In 2006, they accounted for 44.1% of the USA harvested area. Two types of cultivars were introduced. FiberMax cultivars accounted for 26.7% and ‘DP 555BR’ accounted for 17.4% of the USA planted area. FiberMax cultivars have been the primary cause of the recent improvement of fiber length and strength in Texas cottons.