Simple Sequence Repeat Markers for Detecting Sources of Tolerance to PTSL Syndrome in Prunus Persica Rootstocks

Peach tree short life (PTSL) is a severe and complex disease syndrome in the Southeast of the United States that causes significant damage to peach orchards and affects more than 70% of the peach acreage in the region. The ring nematode is known to be one of the major factors strongly associated with the PTSL syndrome. A peach rootstock (Guardian® Brand BY520-9, also referred to as Guardian® or BY520-9), which is tolerant to ring nematode and PTSL, was released in 1994. To investigate the genetic relatedness of PTSL tolerant genotypes and identify possible parents of Guardian® selections as sources of the PTSL tolerance trait, 98 genotypes derived from the BY520-9 pedigree, and others showing different degrees of field resistance or susceptibility to PTSL, were selected for simple sequence repeat analysis. Nineteen of 32 microsatellite loci were polymorphic. Allele number averaged 2.7 per locus with heterozygosity levels ranging from 0.07 to 0.60. Cluster analysis of these genotypes produced a dendrogram in agreement with their putative pedigrees. Thirty-eight F₄ genotypes from Guardian pedigree were used for the parental identification analyses. Of those, nine most likely parental genotypes were identified for 10 field tested F₅ genotypes produced from open-pollinated selections of BY520-9.