Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/10/2004
Publication Date: 6/23/2004
Citation: Sakhanokho, H.F., Ozias-Aikens, P., May, O.L., Chee, P.W. 2004. Induction of somatic embryogenesis and plant regeneration in select Georgia and Pee Dee cotton lines. Crop Science. 44:2199-2205. Interpretive Summary: Since the release of the first commercially available transgenic (genetically engineered) cotton variety in 1996, farmers have been adopting transgenic cotton varieties at a rapid pace. In most southern states, transgenic varieties occupy 80-90% of the acreage in production. However, despite their many advantages, genetically engineered cotton varieties present some problems, including lower yields as compared to local conventional varieties and a potential genetic bottle neck (the varieties are too closely related) due to the uniformity of available transgenic varieties. Currently, the most common method of genetically engineering elite cotton varieties is to first genetically engineer Coker 312, an obsolete and poor cotton variety, and then undertake a 4-6 backcross program to transfer the gene of interest to a chosen elite variety. This is a very long and expensive process which may not eliminate all the undesirable attributes of Coker 312. The main reason why this path is chosen is that, with the exception of the Coker varieties, most cotton varieties do not readily produce somatic embryos in tissue culture, a very crucial step in the cotton genetic engineering process. Therefore, finding elite cotton varieties capable of producing somatic embryos takes on added value. We tested 15 elite Upland cotton varieties for their potential to produce somatic embryos. The varieties were as follows: 8 varieties developed by the Georgia Agriculture Experiment Station and 7 by the USDA-ARS Pee Dee cotton breeding program. We used three tissue culture media that we had previously developed. We were successful in producing plants from somatic embryos in three Pee Dee varieties (PD 97019, PD 97021, and PD 97100) and one Georgia variety (GA 98033). The present results can be used as the stepping stone to genetically engineer these elite Pee Dee and Georgia cotton varieties.
Technical Abstract: The current standard strategy for cotton transforamtion uses Agrobacterium for gene transfer and regeneration via somatic embryogenesis, but it is successful only in a handful of cultivars. This study was undertaken with the prospect of expanding the number of elite Upland cotton genotypes that can be regenerated via somatic embryogenesis. We tested 15 elite Upland cotton lines from Southeast germplasm: 8 lines developed by the Georgia Agriculture Experiment Station and 7 by the USDA-ARS Pee Dee coton breeding program. These genotypes were tested on three embryo initiation/maturation media that were previously found to be capable of inducing somatic embryogenesis in diverse cotton species. Three Pee Dee lines, PD 97019, PD 97021, and PD 97100 and one Georgia line, GA 98033, responded to at least one of the three medium treatments. As expected, the regeneration efficiency of the Georgia and Pee Dee lines was relatively low as compared to the standard Coker 312 cultivar and a high degree of seed-to-seed variability was observed. However, the mean number of somatic embryos (SEs) per gram of tissues was high for the two best embryogenic lines, PD 97019 and GA 98033. Furthermore, the percentage of SEs that converted into plantles for GA 98033 was comparable to Coker 312 in two of the three media tested. These embryogenic Georgia and Pee Dee lines represent the most elite Upland material to-date that can be regenerated via somatic embryogenesis.