Developing Molecular Marker Resources for Pecan

Pecan [Carya illinoinensis (Wangenh.) K. Koch] is a long-lived diploid (2n = 2x = 32) tree species native to the Mississippi River Valley.  Pecan has a complex inheritance pattern and high levels of heterozygosity.  Thus, efforts aimed at characterizing the available germplasm resources to understand the existing genetic variation and opportunities for trait improvement in pecan could be accelerated with the availability of genomic tools.  Although genomic resources in pecan lag behind other major species, progress is being made.  We report here the results of initial collaborative efforts to develop molecular marker resources for pecan. The pecan cultivars evaluated in this study differ in nut characteristics, disease resistance and maturity.  DNA from the cultivars Mahan, Wichita, Kanza and Pawnee (the most widely planted pecan cultivar) was extracted using a modified CTAB method.  PCR was used to amplify genomic regions targeting EST sequences, conserved gene sequences in multiple plant species and simple sequence repeats.  Our initial results demonstrate the feasibility of developing genomic resources for Carya spp. and provide the foundation for their utilization in germplasm characterization and identification of molecular markers linked to traits with practical value.  Ultimately, the genomic resources generated could facilitate selection and implementation of molecular breeding approaches in pecan improvement programs.