USE OF MICROSATELLITE MARKERS TO DEVELOP NEW EASTERN BLACK WALNUT CULTIVARS IN MISSOURI, USA
Eastern black walnut (Juglans nigra L.), is valued both for its edible nuts and high quality timber. Production of black walnut nutmeats is centered in the western portion of the species native range and primarily derived from wild sources. An applied breeding program focused on the development of improved black walnut nut cultivars was initiated at the University of Missouri in 1996. Initially, a base population of 84 nut cultivars was assembled, represented by 161 total trees in three replicated clonal repositories. Microsatellite markers have been repeatedly used to define levels of genetic diversity within this collection, as well as facilitate breeding program activities. All base population trees were fingerprinted using 10 microsatellite markers in 2004. Results suggested that the collection actually contained 61 different cultivars, rather than 84 as originally defined. This 27% error rate was attributed to past propagation errors, due to the fact that most scion sources were obtained from non-commercial sources. These fingerprint results were also compared using phenological descriptors. In cases when two trees shared similar, but not identical fingerprints, date of first pollen shed and first pistillate bloom more accurately reflected actual cultivar differences in comparison to season length and mean pistillate bloom date. To facilitate breeding program goals, microsatellites have been employed to identify full siblings within a large open pollinated seedling family for the purpose of creating the first mapping population for the species. To date, 787 seedlings have been genotyped representing 17 known pollen parents. In addition, microsatellites were used to confirm the parentage of 121 control pollinated seedlings. Overall, for nearly 10% of these hand-pollinated trees (12/121) the assumed parentage was at least partially incorrect, which demonstrates the value of using currently available micro¬satellite fingerprinting techniques to conserve and improve this important hardwood tree species.
Coggeshall, M.V. (2011). USE OF MICROSATELLITE MARKERS TO DEVELOP NEW EASTERN BLACK WALNUT CULTIVARS IN MISSOURI, USA. Acta Hortic. 918, 221-226
Juglans nigra L., nut breeding program, paternity analysis, agroforestry