Resistance Response of the Ma genes from `Myrobalan' Plum to Meloidogyne hapla and M. mayaguensis

Abstract

In `Myrobalan' plum (Prunus cerasifera Ehr.), Ma1 and Ma2 are single major dominant genes that control the resistance to the predominant root-knot nematode (RKN) species Meloidogyne arenaria (Neal) Chitwood, M. incognita (Kofoid & White) Chitwood, and M. javanica (Treub). These genes were evaluated for activity to the northern RKN M. hapla Chitwood and the tropical RKN M. mayaguensis Rammah & Hirschmann, neither of which is controlled by the Mi gene from tomato. This study was conducted under greenhouse conditions using a resistance screening based on high and durable inoculum pressure by the nematodes. Tests were conducted simultaneously for: M. arenaria (as a reference for the Ma genes); M. hapla and M. mayaguensis from crosses segregating for either Ma2 alone or Ma2 and Ma1 and involving the resistant parental clones P.2175 (heterozygous for Ma1) and P.1079 (homozygous for Ma2); and the host parental clone P.2646 (recessive for both Ma genes). Each parental clone and each individual of the segregating progenies reacted in a similar way to M. arenaria and M. mayaguensis, indicating that the Ma genes also control resistance to M. mayaguensis. By contrast, all parental clones and progenies were completely resistant to M. hapla, and, despite high inoculum pressure, no effect of the Ma genes on this species could be established.