Construction of a Genetic Linkage Map for Identification of Molecular Markers Associated with Resistance to Xanthomonas Arboriciola Pv. Pruni in Peach [Prunus Persica (L.) Batsch]

Bacterial spot, caused by Xanthomonas campestris pv. pruni, is a serious disease that can affect peach fruit quality and production. The molecular basis of its tolerance and susceptibility is yet to be understood. To study the genetics of the peach in response to bacterial spot, an F₂ population of 188 individuals from a cross between Clayton, a resistant phenotype, and O’Henry, which is very susceptible to bacterial spot, was created. Four hundred and thirty-two SSR markers already mapped in Prunus were tested for their polymorphism. Only 25% (108) were informative and were used in development of a genetic linkage map. The F₂ population was planted at three locations: the Sandhills Research Station, Jackson Springs, NC; the Sandhill Research and Education Center, Pontiac, SC; and the ARS-USDA Southeastern Fruit and Tree Nut Laboratory at Byron, GA. Field data for response to bacterial spot infection were collected three times a year from two locations, NC and SC. Preliminary data indicate involvement of one or two major genes in peach having resistance to bacterial spot leaf infection. The genetic map in combination with field data will be used to locate the region(s) in the genome associated with bacterial spot resistance. Marker-assisted selection for bacterial spot resistance will be discussed.