High resolution mapping of disease resistance in Prunus

Breeding for disease resistant plants is economically important for crop species. Natural disease resistance is highly desirable because it reduces the reliance on chemical control of pests and pathogens in the field. The Rosaceae encompasses some of the world's most economically important fruit tree species. Many of these fruit tree species, Prunus (apricot, peach, plum and cherry), Malus (apple), Pyrus (pear), and Fragaria (strawberry) require heavy pesticide use. Therefore, Prunus breeding programs would greatly benefit from the introduction of natural resistance. In order accomplish this; identification of resistant sources is required. Phenotypic screening of resistant germplasm is extremely time consuming, labor intensive, and costly. Marker assisted selection (MAS) could substantially streamline the screening process; however, MAS requires molecular markers tightly associated with the resistance trait.; To identify regions of resistance in the Prunus genome, we used peach and apricot BAC libraries, the Prunus genetic reference map (Aranzana et al., 2003; Dirlewanger et al., 2004) and the peach physical map (www.rosaceae.org). We developed a resistance map for Prunus that currently contains 42 map locations for putative resistance regions distributed among 7 of the 8 linkage groups of Prunus. Additionally we constructed a genetic map for apricot breeding which identifies a locus for PPV resistance. Genetic markers flanking this region were identified and need to be further evaluated for their use in MAS.; This work presents several applications of these tools: (1) the development of a resistance gene map for Prunus to assist in MAS for important disease resistance traits, (2) the construction of a genetic map for apricot breeding and the identification and characterization of sharka resistance loci, and (3) the evaluation of specific molecular markers associated with Sharka resistance and their implementation in MAS disease resistance breeding.