XVI International Botanical Congess
We have used the natural variation in Arabidopsis populations as a source of polymorphisms in genes controlling light response. Hypocotyl lengths of 140 Arabidopsis ecotypes were measured in white, blue, red, and far red light treatments. Response to gibberilic acid and brassinazole phytohormones was also measured. A wide range of responses was observed. In some cases, variation between ecotypes suggested changes in specific photoreceptor signaling pathways. Ler/Cvi RILs were also surveyed and QTL analysis was performed. At least 3 major QTLs were identified in each of 6 treatments. A QTL on Chromosome 1 was responsible for 40% of the variation in white, blue, and red light. Crosses have been initiated to isolate individual loci with the hope of cloning the genes responsible for the phenotypic variation. Sequence variation at the PHYB locus is also presented.