Sri Lankan wild rices: a rich source of natural resistance against the rice root knot nematode

Meloidogyne graminicola (Mg) is a major nematode pest threatening global rice production, and natural resistance in cultivated rice is limited. This study examined 34 Sri Lankan wild rice accessions to identify new resistance sources. Seven accessions showed strong resistance based on low gall formation: five from the endemic species Oryza rhizomatis (IRGC 105443, 105448, 103417, 103410, 103421), one O. nivara (IRGC 103415), and one O. rufipogon (IRGC 105420). Most resistant accessions originated from the Dry Zone Low Country, except for the O. rufipogon accession from the Wet Zone Low Country. The high frequency of resistance in O. rhizomatis suggests unique evolutionary adaptations, while resistance in O. nivara—which shares the AA genome with cultivated rice—may have introgressed into northern O. sativa populations. These findings indicate Sri Lanka could represent an evolutionary hotspot for Mg resistance, warranting further genetic characterisation of these accessions.