Identification of Heat Tolerance in Cotton Using Chlorophyll Fluorescence

Heat stress adversely affects upland cotton (Gossypium hirsutum L.) production in the US.  Using chlorophyll fluorescence has been proposed as a method of evaluating heat tolerance. The objective of this research is to use chlorophyll fluorescence as a tool for finding elite wild accessions with heat tolerance. Based on initial screenings, forty-four accessions were identified with heat tolerance (Frederick, 2006). We tested chlorophyll fluorescence on these forty-four selected accessions under heat stress (24 h at 45 °C) in a growth chamber. Five elite accessions turned out to be significantly more heat tolerate than commercial cultivars. A field evaluation using chlorophyll fluorescence was conducted on these five elite wild accessions at different stages of growth. The same result was found that these five elite accessions had higher fluorescence values than the commercial cultivars throughout the growth season.