MICROSATELLITE AND PHENOLOGICAL DESCRIPTORS IDENTIFY EASTERN BLACK WALNUT CULTIVARS IN MISSOURI, USA

Abstract

An applied breeding program focused on the improvement of eastern black walnut (Juglans nigra) for edible nut production was initiated at the University of Missouri in 1996. Eighty four cultivars were grown as 158 trees in three replicated clonal repositories. Beginning in 2003, the collection was characterized using seven phenological descriptors: date of budbreak, first pistillate bloom, peak pistillate bloom, first pollen shed, peak pollen shed, nut harvest date and season length. In 2004, all trees were further characterized using 10 microsatellite markers. Genetic fingerprinting showed that the collection contained 57 cultivars rather than the expected 84, which we attribute to past propagation errors. Fingerprinting results generally agreed with the phenological data. The utility of phenological data for discriminating genotypes was affected by specific descriptor and tree size. First pistillate bloom, first pollen shed and season length calculated on a date basis had the smallest coefficients of variation for the seven phenological descriptors used in this study.