Project Number: 6208-21000-016-06
Project Type: Reimbursable

Start Date: Jan 01, 2008
End Date: Dec 31, 2008

Objective:
(1) Evaluate pollen composition to identify genetic differences associated with observed differences in dehydration sensitivity. (2) Evaluate the impact of the differences on gene flow under irrigated and dryland conditions. (3) Evaluate the timing of pollen dehiscence among the lines to determine if delays in dehiscence may influence overall pollen viability. (4) Evaluate stigma recognition of dehydration sensitive versus dehydration resistant pollen. (5) Evaluate a range of lines to determine the range of resistance to pollen dehydration existing in our germplasm collections.

Approach:
(1) Initial characterization of potential differences in pollen composition will focus on components of cuticular waxes and on potential osmolytes. Data to date suggests more than one mode of resistance to water loss from the pollen. It is possible that some resistance is associated with cuticular barriers, while another resistance may be related to osmotic differences. Standard GC and HPLC analyses will be performed to evaluate lipid and osmolyte characteristics. (2) Gene flow analyses will look at movement into DP565 and PHY72 under irrigated and dryland field conditions. The dominant anthocyanin marker associated with De Ridder Red cotton will be used in the evaluation. Seeds will be harvested from plots surrounded by the "red" cotton, and the percent "red" seedlings determined following germination. Gene flow away from the PHY72 and DP565 will be evaluated by surrounding these lines with Gregg 65 (a glandless line). The recessive trait allows us to screen for glanded offspring as we sample various distances from the PHY72 or DP565 plots. (3) The timing of pollen dehiscence will be evaluated initially in greenhouse-grown plants by harvesting flowers throughout the morning and determining the percent dehiscent anthers. Pollen viability will also be evaluated using our in vitro pollen germination bioassay. (4) Stigma recognition of dehydration sensitive versus dehydration resistant pollen will be evaluated by co-pollination of a transgenic Coker 312 and each of the six test lines onto stigmas of all seven lines. Following fertilization, seeds will be harvested, germinated, and PCR analyses used to determine the percent Coker 312 pollinated seeds. (5) A collection of commercial and converted lines will be analyzed for the time to first pollen grain popping in 0.8 M sucrose. This study will aid in identifying the range of pollen dehydration resistance within germplasm collections. IBC RECERTIFICATION SEPTEMBER 2, 2008.