Association mapping of leaf traits, flowering time, and phytate content in Brassica rapa

Association mapping was used to investigate the genetic basis of variation within Brassica rapa, which is an important vegetable and oil crop. We analyzed the variation of phytate and phosphate levels in seeds and leaves and addi- tional developmental and morphological traits in a set of diverse B. rapa accessions and tested association of these traits with AFLP markers. The analysis of population structure revealed four subgroups in the population. Trait values differed between these subgroups, thus defining associations between population structure and trait values, even for traits such as phytate and phosphate levels. Marker-trait associations were investigated both with and without taking population structure into account. One hundred and seventy markers were found to be associated with the observed traits without correction for population structure. Association analysis with correction for population structure led to the identification of 27 markers, 6 of which had known map positions; 3 of these were confirmed in additional QTL mapping studies.