Submitted to: Plant Cell Tissue and Organ Culture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/20/2004
Publication Date: 2/4/2005
Citation: Sakhanokho, H.F., Ozias-Akins, P., May, O.L., Chee, P.W. 2005. Putrescine enhances somatic embryogenesis and plant regeneration in upland cotton. Plant Cell Tissue And Organ Culture 81:91-95. Interpretive Summary: One of the main problems facing cotton genetic engineering is the scarcity of cultivars or varieties that are capable of readily producing somatic embryos. For this reason, current commercial transgenic or genetically modified cotton cultivars/varieties generally derive from Coker 312. This has the potential for creating a genetic bottleneck despite extensive backcrossing. In order to expand the number of elite Upland cotton genotypes that can be regenerated via somatic embryogenesis, we previously tested 15 elite Upland cotton lines from Southeast germplasms: 8 lines developed by the Georgia Agriculture Experiment Station and 7 by the USDA-ARS Pee Dee cotton breeding program. 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. Our objective in this study was to improve the capability of the newly tested varieties to produce somatic embryos. We tested several concentration of putrescine (Put), a high nitrogen compound, on our previously developed regeneration media. The best results were obtained with the -Naphthalene acetic acid (NAA)-based treatments, S15g.05NAA and EMMS2, as compared to the 2,4-Dichlorophenoxyacetic acid (2,4-D)-based medium, EMMS4. Inclusion of 0.5 mg l-1 Put improved SE production for most treatments and genotypes tested. An 8- and 2-fold improvement was achieved in SE production on the EMMS2-0.5Put treatment as compared to EMMS2 alone for cotton genotypes PD 97019 and GA 98033, respectively. A dramatic increase in somatic embryo number (53-fold) was obtained with the addition of 0.5 mg l-1 Put to EMMS2 for the genotype PD 97021, which was essentially recalcitrant without Put treatment. Conversion of SEs into plants was both genotype- and medium-dependent. These improved results can make it possible to directly transform or genetically engineer these Pee Dee and Georgia cotton lines.
Technical Abstract: An efficient plant transformation system depends, in large part, on the capability of the cells to produce somatic embryos (SEs) and to then produce plants. Improvement in somatic embryogenesis has been achieved in several Georgia and Pee Dee cotton lines with media containing various putrescine (Put) concentrations. The best results were obtained with the Naphthalene acetic acid (NAA)-based treatments, S15g. 05NAA and EMMS2, as compared to the 2,4- Dichlorophenoxyacetic acid (2,4-D)-based medium, EMMS4. Inclusion of 0.5 mg 1-1 Put improved SE production for most treatments and genotypes tested. An 8- and 2-fold improvement was acheived in SE production on the EMMS2-0.5 Put treatment as compared to EMMS2 alone for cotton lines PD 97019 and GA 98033, respectively. A dramatic increase in SE number (53-fold) was obtained with recalcitrant without Put treatment. Conversion of SEs into plants was both genotype- and medium-dependant. These results could pave the way for the direct transformation of these elite Georgia and Pee Dee cotton lines for transgenic cultivar development.