Heredity and genetic mapping of domestication-related traits in a temperate japonica weedy rice

Rice is often found as various weedy forms in temperate or newly cultivated rice growing regions throughout the world. The emergence of these forms in the absence of true wild rice remains unclear. A genetic analysis of domes tication-related traits (weed syndrome) has been conducted to better unders tand the appearance of these plants in rice fields. A doubled haploid (DH) population was derived from a cross between a japonica variety and a weedy plant collected in Camargue (France) to set up a genetic linkage map consis ting of 68 SSR and 31 AFLP loci. Five qualitative traits related to pigment ation of different organs and 15 developmental and morphological quantitati ve traits were scored for genes and QTLs mapping. Despite a good reactivity in anther culture and a high fertility of the DH lines, segregation distor tions were observed on chromosomal segments bearing gametophytic and steril ity genes and corresponded to various QTLs evidenced in indica x japonica d istant Crosses. Mapping of the coloration genes was found to be in agreemen t with the presence of several genes previously identified and according to the genetic model governing the synthesis and distribution of anthocyan pi gment in the plant. In addition, the main specific traits of weedy forms re vealed the same genes/QTLs as progeny derived from a cross between Oryza sa tiva and its wild progenitor O. rufipogon. A large variation for most chara cters was found in the DH population, including transgressive variation. Si gnificant correlations were observed between morphology and traits related to weeds and corresponded to a distinct colocalization of most of the QTLs on a limited number of chromosomal regions. The significance of these resul ts on the origin of weedy forms and the de-domestication process is discuss ed.