Analysis of the root-knot nematode (Meloidogyne incognita) resistance and Ma gene cloning in Xinjiang wild (Prunus sogdiana) myrobalan plums

Abstract

Wild plant resources represent a major source of important stress-resistance genes. We previously collected Xinjiang wild myrobalan plum (Prunus sogdiana) seeds from the wild natural forest in Daxigou, Huocheng County, Xinjiang, China and cultivated 139 individual P. sogdiana plants. After many years of scoring the resistance of these myrobalan plum plants to a root-knot nematode (RKN; Meloidogyne incognita), we identified stably resistant and susceptible plants. In this study, we used six resistant and six susceptible plants to identify molecular markers closely linked to the RKN resistance gene, Ma, and to investigate the characteristics of this gene in P. sogdiana. Of the two SCAR markers closely linked to the Ma gene, SCAL19690 was present in both resistant and susceptible plants, whereas SCAFLP2202 was not present in resistant or susceptible individuals, indicating that SCAL19690 and SCAFLP2202 could not be used as tools to screen for RKN resistance conferred by the Ma gene in P. sogdiana. We cloned the Ma gene and identified a stop codon at 523 bp in the mRNA of both resistant and susceptible individuals, which only encodes a 174-amino acid polypeptide in P. sogdiana due to premature translational termination, indicating that the Ma protein in P. sogdiana is incomplete. These results indicate that the Ma gene in Xinjiang wild myrobalan plum is different from that of European Myrobalan plum (P. cerasifera), demonstrating that wild myrobalan plum accessions of different origins represent rich, diverse genetic resources of resistance to M. incognita.