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ARS Home » Plains Area » College Station, Texas » Southern Plains Agricultural Research Center » Crop Germplasm Research » Research » Publications at this Location » Publication #417702
Research Project: Pecan Breeding and Management of the National Collection of Carya Genetic Resources

Location: Crop Germplasm Research

Title: Quantitative trait loci for bearing habit in a 'Sparrow’ x 'Schessler' Juglans nigra mapping population

Author
item JABLONSKI, BENJAMIN - University Of Missouri System
item MEIER, NICHOLAS - University Of Missouri System
item Chatwin, Warren
item COGGESHALL, MARK - University Of Missouri System
item ROMERO-SEVERSON, JEANNE - University Of Notre Dame
item REVORD, RONALD - University Of Missouri System

Submitted to: Tree Genetics and Genomes
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/13/2024
Publication Date: N/A
Citation: N/A

Interpretive Summary: The USDA Pecan Breeding and Genetics Program regularly checks different features of pecan nuts, like their size, shape, and color, as well as what's inside them. Walnuts are cousins to pecan, and the most closely related commercial tree-nut crop. This research identified genetic regions that contributed to the ability for developing tight clusters of walnut fruit on compact branches, called spur-bearing. Spur-bearing eastern black walnuts have increased nut yields and a shorter juvenile period before nut production. While spur-bearing has not been observed in pecan, these genetic regions could be examined in pecan to see if similar connections with increased yield or shorter juvenile periods exist.

Technical Abstract: Eastern black walnut, Juglans nigra L., is an economically important tree species valued for its high-quality timber and edible nuts. A regional industry for the species' nut and kernel products resides in Missouri, where over 9 million kg of hulled in-shell nuts are purchased in masting years. The crop is primarily based upon nuts harvested from wild trees, placing a ceiling on nut volume and quality (e.g., 10-14% kernel, small, dark kernels). Orchards of named cultivars, like 'Kwik Krop' and 'Sparrow', supply up to 22,000 kilograms of nuts with a higher kernel percentage (>26%) and quality. Such cultivars often represent chance wild or on-farm seedlings, clonally propagated since the late 1800's by enthusiasts. Today, continued improvement of eastern black walnut as an orchard crop is limited by a long generation time, delayed expression of selection criteria, and space requirements – creating a strong need for marker-trait association studies that inform progeny selection. The first linkage map for J. nigra was recently created using the 'Sparrow' × 'Schessler' F1 population and loci for phenology traits discovered. The objective of this study is to utilize these genetic resources to detect quantitative trait loci (QTL) and report associated DNA markers for the spur-bearing habit, which promotes precociousness and high yield. Using single-year data from the 11-year-old population, we observe that segregation for the spur-bearing habit appears dihybrid-like, and three QTLs (p > 0.99) were identified on linkage group (LG) 8, LG11, and LG16 that explain 7.2%, 8.7%, and 10% of trait variation, respectively. Regions between flanking DNA markers were 3.16 cM, 4.32 cM, and 9.69 cM, respectively. This study is the first to examine the genetic control of bearing habit and yield in eastern black walnut and informs breeders’ approach for their future genetic improvement.