Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: July 7, 2012
Publication Date: July 7, 2012
Citation: Mittal, A., Payton, P.R., Ritchie, G., Burke, J.J., Rock, R. 2012. Field testing of transgenic cotton expressing Arabidopsis ABA INSENSITIVE5 and B3- domain related to ABI3/VIVIPAROUS1 (RAV) transcription factors [abstract]. Meeting Abstract. P. 601. Technical Abstract: We conducted field trials for ABI5 and RAV transgenics under the most extreme heat and drought conditions on record. The data validate greenhouse experiments that show AtRAV1 and AtRAV2 overexpression results in an average of 9% increases in fiber length without yield penalty and with greater gin turnout, improved fiber qualities of maturity and uniform fineness under both non-stressed and extreme abiotic stress conditions. Several other transgenic events showed longer fibers in well-watered conditions. At least one transgenic event from ABI5, RAV1, RAV2L and RAV2 (two events) maintained higher photosynthesis and water use efficiency (WUE) throughout extended drought stress treatments in the greenhouse and field, which we hypothesize is channeled to sink tissues to increase assimilate deposition during flowering and fiber development. Increases in leaf area and mass correlate with improved photosynthesis and WUE, supporting the hypothesis that a greater source of photosynthate benefits fiber development (the major sink for assimilate) and results in improved fiber quality. RAV2 and RAV1 transgenics have delayed flowering and boll cracking in both unstressed and drought-stress conditions, effectively extending the cut-out and maturation stages. Such a physiological adaptation is suggestive of a 'less-stressed' phenotype, supported by the physiological and biomass data and increased internode lengths and branching of transgenics, consistent with others’ studies of RAVs in Arabidopsis, pepper, chestnut, and poplar. We have evidence from greenhouse drought stress experiments that 'stacking' ABI5 and RAV transgenic events provides a synergistic degree of drought avoidance and increased root biomass than single events. Ongoing experiments are focused on characterization of seed protein and oil, and root/shoot biomass partitioning as mechanisms of drought avoidance. We are testing the hypothesis that delayed flowering/increased branching and improved fiber qualities in the transgenics are due to altered expression of Gh-FLOWERING LOCUS T and GhMYB25-Like and homologous transcription factors, respectively.