Target-Site Mutations and Expression of Gene Copies Vary According to Species.

The sustainability of rice cropping systems is jeopardized by the large number and variety of populations of polyploid spp. resistant to ALS inhibitors. Better knowledge of the species present in Italian rice fields and the study of genes involved in target-site resistance could significantly contribute to a better understanding of resistance evolution and management. Using a CAPS- molecular marker, two species, (L.) P. Beauv. and (Vasinger) Vasing., were identified as the most common species in rice in Italy. Mutations involved in ALS inhibitor resistance in the different species were identified and associated with the homoeologs. The relative expression of the gene copies was evaluated. Molecular characterization led to the identification of three genes in and two in . The two species also carried different point mutations conferring resistance: Ala122Asn in and Trp574Leu in . Mutations were carried in the same gene copy (), which was significantly more expressed than the other copies ( and ) in both species. These results explain the high resistance level of these populations and why mutations in the other copies are not involved in herbicide resistance.