Resources for genetic control of the root-knot nematode Meloidogyne enterolobii, an impending threat to direct-seeded rice agriculture

Due to global climate change and water scarcity, direct-seeded rice (DSR) cultivation is increasingly being adopted in drought-prone states of India. However, greater nematode incidence is a major concern in DSR agroecosystems. In recent years, a nematode of quarantine status, Meloidogyne enterolobii, has developed increased virulence relative to other root-knot nematode (RKN) species in different crop plants. In the current study, we screened 40 widely grown rice (Oryza sativa) cultivars that suit different agroecosystems (including DSR, irrigated, and both DSR/irrigated systems) for M. enterolobii infectivity. M. enterolobii displayed a fast life cycle progression in rice with reproductive biology (deposited egg mass extruding out of the root epidermis) adaptive for aerobic rice production systems. While exploring the potential sources of resistance to M. enterolobii for future rice breeding programs, we identified the wild relative of rice O. nivara to be highly resistant to M. enterolobii infection. O. nivara carried an allele of the MG1 gene, whose expression was upregulated strongly upon M. enterolobii infection. The role of MG1 in conferring resistance to M. enterolobii was tested by overexpressing the allele in susceptible O. sativa japonica cultivar Taipei309. Since M. enterolobii has already spread to different states in India, it is an impending threat to rice agriculture especially in DSR practices. Our study presents useful resources for genetic control of M. enterolobii in DSR agriculture.