QTL MAPPING OF NATURALLY-OCCURRING VARIATION IN FLOWERING TIME OF ARABIDOPSIS-THALIANA

A segregating F-2? population of Arabidopsis thaliana derived from a c ross between the late-flowering ecotype Hannover/Munden (HM) and the e arly-flowering ecotype Wassilewskija (WS) was analyzed for flowering t ime and other morphological traits. Two unlinked quantitative trait lo ci (QTLs) affecting days to first flower (DFF-a and DFF-b) mapped to c hromosome 5. QTLs which affect node number (NN), leaf length at flower ing (LLF), and leaf length at 35 days (LL35) also mapped to chromosome 5; LLF-a, LL35-a, NN-a map to the same region of chromosome 5 as DFF- a; LLF-b and LL35-bmap to the same region of chromosome 5 as DFF-b. An other QTL affecting leaf length at flowering (LLF-c) maps to chromosom e 3. The proximity of DFF-a, LLF-a, LL35-a and NN-a, as well as the si milarity in gene action among these QTLs (additivity), suggest that th ey may be pleiotropic consequences of a single gene at this locus. Sim ilarly, LL35-b and LLF-b map near each other and both display recessiv e gene action, again suggesting the possibility of pleiotropy. DFF-b, which also maps near LL35-b and LLF-b, displays largely additive gene action (although recessive gene action could not be ruled out). This s uggests that DFF-b may represent a different gene from LL35-b and/or L LF-b. DFF-a maps near two previously identified mutants: co (which als o affects flowering time and displays gene action consistent with addi tivity) and flc. Similar map locations and gene actions of QTLs affect ing the correlated traits DFF, LLF, LL35 and NN suggest that these gen omic regions harbor naturally occurring allelic variants involved in t he general transition of the plant from vegetative to reproductive gro wth.