085 Development of a Cleaved Amplified pPolymorphic Sequence (CAP) and Restriction Fragment Length Polymorphisms (RFLPs) Linked to the Mi Root-knot Nematode (Meloidogyne incognita, race 1) Resistance Gene in Peach [Prunus persica (L.) Batsch]
Peach rootstock breeding may be accelerated by utilization of molecular markers linked to the root-knot nematode resistance locus (Mi) to screen segregating populations. A genetic linkage map was constructed using RFLP markers in an F2 population (PMP2) that is segregating for this locus. PMP2 is derived from a controlled cross of the relatively diverse peach rootstocks Harrow Blood (susceptible) and Okinawa (homozygous resistant). Bulked Segregant Analysis was applied using RAPD markers. A single small (227 base pairs) RAPD marker was found to be linked to the dominant resistant allele of Mi at a distance of 10 cM. This new marker joined the Mi locus to the RFLP linkage map and showed that two dominant RFLP markers are located between the RAPD marker and Mi. RFLPS are expensive, time-consuming and RAPD markers are unreliable, and therefore both are unsuitable for screening breeding populations. We attempted to convert the RAPD marker to a more breeder-friendly CAPS marker. The converted CAP marker was dominant. Attempts to convert the CAP marker to a co-dominant marker were not successful. The utility of the CAP marker was tested in an open pollinated F2 population derived from the F1 parent of PMP2 and in several rootstocks. The genetic linkage map was compared to other Prunus maps. The PMP2 linkage group containing the Mi locus can be related to the peach × almond linkage group which contains the phosphoglucomutase Pgm-1 locus.
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