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Abstract

To discover new loci controlling flowering time in natural populations, we have analyzed the flowering time of a recombinant inbred line (RIL) population derived from crosses of Niederzenz (Nd-1) to Columbia (Col-3 and Col-5; Holub, et al., Adv. Bot. Res. 24[1997]). In short days, the 96 RILs show a wide range of flowering times and QTL analysis detects four significant QTL responsible for this variation: a major QTL, termed FLOWERING1, on the bottom of chromosome 1; two QTL on chromosome 2; and one QTL on chromosome 5. FLOWERING1 maps very close to FLM/MAF1, a gene encoding a MADS-domain transcription factor that has been shown by the Amasino and Riechmann labs to have flowering time effects in both long and short days. Additionally, the phenotypes of flm-1 and flm-2, two T-DNA alleles isolated in the Ws background, agree well with that of FLOWERING1. Upon attempting to sequence the FLM gene from Nd-1, we discovered a 6.8 kb deletion removing the entire coding region. In support of FLM being FLOWERING1, fine-mapping experiments have located the QTL to a 140 kb interval containing FLM. Out of 140 accessions analyzed, only one additional accession from Niederzenz shares this deletion. However, further analysis of the FLM genomic region from more accessions revealed significant polymorphism, including transposon insertion events, the nature and consequences of which will be presented.