At least two mechanisms underlie this incompatibility; the succinoglycan of this strain does not appear to correctly promote infection in A17 (Simsek et al., 2007) and the isoforms of NCR peptides NFS1/NFS2 in this accession preclude symbiosis (Wang et al., 2017; Yang et al., 2017). This evidence concerns the gene NFS1 and infection.