Quantitative trait loci for floral morphology in Arabidopsis thaliana

A central question in biology is how genes control the expression of quanti tative variation. We used statistical methods to estimate genetic variation in eight Arabidopsis thaliana floral characters (fresh flower mass, petal length, petal width, sepal length, sepal width, long stamen length, short s tamen length, and pistil length) in a cosmopolitan sample of 15 ecotypes. I n addition, we used genome-wide quantitative trait locus (QTL) mapping to e valuate the genetic basis of variation in these same traits in the Landsber g erecta X Columbia recombinant inbred line population. There was significa nt genetic variation for all traits in both the sample of naturally occurri ng ecotypes and in the Let X Col recombinant inbred line population. In add ition, broad-sense genetic correlations among the traits were positive and high. A composite interval mapping (CIM) analysis detected 18 significant Q TL affecting at least one floral character. Eleven QTL were associated with several floral traits, supporting either pleiotropy or tight linkage as ma jor determinants of flower morphological integration. We propose several ca ndidate genes that may underlie these QTL on the basis of positional inform ation and functional arguments. Genome-wide QTL mapping is a promising tool for the discovery of candidate genes controlling morphological development , the detection of novel phenotypic effects for known genes, and in generat ing a more complete understanding of the genetic basis of floral developmen t.