APPLICATION OF MOLECULAR MARKERS IN THE DEVELOPMENT OF PEACH ROOTSTOCKS TOLERANT TO RING NEMATODE (MESOCRICONEMA XENOPLAX)

Abstract

Peach Tree Short Life (PTSL) is a severe disease syndrome in the southeastern United States causing significant damage to peach orchards. Ring nematode is intimately associated with the PTSL syndrome. Recently, a peach rootstock (GuardianTM Brand BY520-9), which is tolerant to ring nematode, was released. The genetic nature of this tolerance, however, is not known. To investigate the genetic relatedness of ring nematode tolerant genotypes and identify possible sources of the tolerance trait, 100 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 thirty-two microsatellite loci were polymorphic. Allele number averaged 2.7 per locus with heterozygosity levels of 0.07 to 0.60. Cluster analysis of these genotypes produced a dendrogram in agreement with their putative pedigrees. The most likely parents with LOD scores of 2.91 to 7.91 were identified for 10 field resistant genotypes produced from open-pollinated selections of ‘BY520-9’ using the program Cervus 1.0.