Black Walnut Breeding Program

---

BLACK WALNUT BREEDING

Over the last 20 years, numerous genetic resources were developed at the University of Missouri Center for Agroforestry to improve eastern black walnut (Juglans nigra) for nut and kernel production. These resources include the first black walnut mapping population, a full-sibling diallel population, and a diverse collection of elite breeding parents. Altogether these resources inform our breeding efforts to develop precocious, consistently high-yielding individuals that have a high percentage of kernels and a mild flavored.

Key Personnel: PI Ron Revord, Adjunct Faculty Mark Coggeshall, Senior Research Specialist Nick Meier, Senior Research Specialist J. Bryan Webber

Master’s students: Benjamin Bishop and Benjamin Jablonski 

BLACK WALNUT MAPPING POPULATION

Research involving the black walnut mapping population of ‘Sparrow’ x ‘Schessler’ saw milestone progress this year. Colleagues at Notre Dame completed the population’s linkage map – where 356 SNP markers and 62 EST-SSR markers and 282 offspring were mapped. Additionally, MS students, Ben Bishop and Ben Jablonski, began collecting a host of detailed phenotypic data on these trees, including nut quality, yield parameters, anthracnose disease screening, and flowering patterns. Further, Purdue colleagues began implementing an assay for host preferences by the walnut twig beetle, which causes thousand canker’s disease. The students will utilize the new linkage map and phenotypic data in quantitative trait loci mapping, starting this winter, to study the genetic basis of these traits and to find closely linked DNA markers that aid selection of the breeding program’s new offspring.

DIALLEL MAPPING POPULATION

The diallel mapping population is composed of eight parent cultivars and 30 full-sibling families, where the combining ability of parents and trait inheritance can be studied. M.S. students Ben Bishop and Ben Jablonski are also studying this population, phenotyping trees similarly to the mapping population.

BLACK WALNUT BREEDING

In spring of 2020, the first black walnut controlled-crosses were made since 2006. Controlled crosses in black walnut are notorious for low success rate, however, encouraging amounts of viable seed were produced this year by refining the pollination technique. We hope to continue improving pollination methods in 2021.

​Controlled crosses are made high in the canopy of mature trees using a bucket truck lift. Targeted branches are covered with white pollination bags after the pollen is applied to receptive flowers.