Walnut Scion & Rootstock Improvement
Walnut Scion & Rootstock Improvement
Walnut Scion & Rootstock Improvement
University of California
Walnut Scion & Rootstock Improvement

Obj. 1: Identify Pathogen-Resistant Germplasm

Identify and characterize Juglans germplasm resistant to key soil-borne pathogens.

Walnut breeders, geneticists, and pathologists are collaborating to propagate full-sib mapping populations for replicated pathogen testing and mapping genetic loci mediating disease resistance.

Preliminary work:

  • A diverse and promising group of wild Juglans spp. has been identified to aid discovery of novel sources of resistance to the major soil-borne diseases.

Assembly of full-sib interspecific hybrid mapping populations:

  • Mother trees segregating for resistance to one or more diseases are being hybridized with J. regia ‘Serr’ to produce F1 interspecific hybrid mapping populations.

Clonal propagation:

  • Hybrid progeny from multiple mother trees are being clonally propagated using in vitro propagation methods to produce suitable numbers of clonal plantlets for replicated greenhouse and field testing against multiple pathogens.

Pathogen screening:

  • The Disease Resistance Evaluation Team will complete field and greenhouse-based replicated resistance testing against multiple pathogens.


  • Promising individuals from the mapping populations will be clonally propagated and advanced to large scale field trials.
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