MARKER-ASSISTED SELECTION OF THE MA GENE FROM MYROBALAN PLUM FOR A COMPLETE-SPECTRUM ROOT-KNOT NEMATODE (RKN) RESISTANCE IN PRUNUS ROOTSTOCKS

Abstract

In Myrobalan plum (Prunus cerasifera; subgenus Prunophora), the clones P.2175, P.1079 and P.2980 are highly resistant to all tested RKN nematodes including Meloidogyne arenaria, M. incognita, M. javanica and also an unclassified isolate Meloidogyne sp. Florida (FL) that overcomes the resistance in other commonly used Prunus sources from the Amygdalus subgenus. All three clones carry a single major dominant gene (alleles respectively designated Ma1, Ma2 and Ma3) that confers a high-level and complete-spectrum resistance (including at least M. arenaria, M. incognita, M. javanica, the Florida isolate and M. mayaguensis). Bulked segregant analysis associated with the RAPD or AFLP techniques were performed to detect markers linked to Ma1 using segregating intra- and interspecific progenies from P.2175 (Ma1ma1) crossed by several host parents (ma ma). Three RAPD, one AFLP and three SSR markers were obtained. From these, one RAPD and one AFLP markers, converted into reliable SCAR (sequence characterized amplified region) markers, were located at less than 1 cM from the gene. One of them (SCAL19) has been evaluated for MAS in an European rootstock program based on Myrobalan plum x Amygdalus (peach, almond or almond-peach) hybrids and proved to be usable reliably in particular to detect the Ma alleles in segregating progenies involving Amygdalus resistance sources such as the peach Nemared, the wild peach P. davidiana, the almond Alnem or the almond-peach hybrids GF.557 and Garfi x Nemared. Data from RFLP and SSR markers, from a reference Prunus map initiated by a European mapping group, indicate that Ma1 is located on the linkage group 7.